| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oldssno | ⊢ (  O  ‘ (  bday  ‘ 𝑋 ) )  ⊆   No | 
						
							| 2 | 1 | sseli | ⊢ ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  →  𝑥  ∈   No  ) | 
						
							| 3 | 2 | 3ad2ant2 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑥  ∈   No  ) | 
						
							| 4 |  | simp1l1 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑋  ∈   No  ) | 
						
							| 5 |  | simp1l2 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑌  ∈   No  ) | 
						
							| 6 |  | simp3 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑥  <s  𝑋 ) | 
						
							| 7 |  | simp1r | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑋  <s  𝑌 ) | 
						
							| 8 | 3 4 5 6 7 | slttrd | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  𝑥  <s  𝑌 ) | 
						
							| 9 | 8 | 3exp | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  →  ( 𝑥  <s  𝑋  →  𝑥  <s  𝑌 ) ) ) | 
						
							| 10 | 9 | imdistand | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑌 ) ) ) | 
						
							| 11 |  | fveq2 | ⊢ ( (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 )  →  (  O  ‘ (  bday  ‘ 𝑋 ) )  =  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) | 
						
							| 12 | 11 | 3ad2ant3 | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  (  O  ‘ (  bday  ‘ 𝑋 ) )  =  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) | 
						
							| 13 | 12 | adantr | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  (  O  ‘ (  bday  ‘ 𝑋 ) )  =  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) | 
						
							| 14 | 13 | eleq2d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ↔  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) ) | 
						
							| 15 | 14 | anbi1d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑌 )  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) ) ) | 
						
							| 16 | 10 15 | sylibd | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  →  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) ) ) | 
						
							| 17 |  | leftval | ⊢ (  L  ‘ 𝑋 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 } | 
						
							| 18 | 17 | a1i | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  (  L  ‘ 𝑋 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 } ) | 
						
							| 19 | 18 | eleq2d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  L  ‘ 𝑋 )  ↔  𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 } ) ) | 
						
							| 20 |  | rabid | ⊢ ( 𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 }  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 ) ) | 
						
							| 21 | 19 20 | bitrdi | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  L  ‘ 𝑋 )  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 ) ) ) | 
						
							| 22 |  | leftval | ⊢ (  L  ‘ 𝑌 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 } | 
						
							| 23 | 22 | a1i | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  (  L  ‘ 𝑌 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 } ) | 
						
							| 24 | 23 | eleq2d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  L  ‘ 𝑌 )  ↔  𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 } ) ) | 
						
							| 25 |  | rabid | ⊢ ( 𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 }  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) ) | 
						
							| 26 | 24 25 | bitrdi | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  L  ‘ 𝑌 )  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) ) ) | 
						
							| 27 | 16 21 26 | 3imtr4d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( 𝑥  ∈  (  L  ‘ 𝑋 )  →  𝑥  ∈  (  L  ‘ 𝑌 ) ) ) | 
						
							| 28 | 27 | ssrdv | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  (  L  ‘ 𝑋 )  ⊆  (  L  ‘ 𝑌 ) ) | 
						
							| 29 |  | sltirr | ⊢ ( 𝑌  ∈   No   →  ¬  𝑌  <s  𝑌 ) | 
						
							| 30 | 29 | 3ad2ant2 | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ¬  𝑌  <s  𝑌 ) | 
						
							| 31 |  | breq1 | ⊢ ( 𝑋  =  𝑌  →  ( 𝑋  <s  𝑌  ↔  𝑌  <s  𝑌 ) ) | 
						
							| 32 | 31 | notbid | ⊢ ( 𝑋  =  𝑌  →  ( ¬  𝑋  <s  𝑌  ↔  ¬  𝑌  <s  𝑌 ) ) | 
						
							| 33 | 30 32 | syl5ibrcom | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( 𝑋  =  𝑌  →  ¬  𝑋  <s  𝑌 ) ) | 
						
							| 34 | 33 | con2d | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( 𝑋  <s  𝑌  →  ¬  𝑋  =  𝑌 ) ) | 
						
							| 35 | 34 | imp | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ¬  𝑋  =  𝑌 ) | 
						
							| 36 |  | simpr | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) ) | 
						
							| 37 |  | lruneq | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  =  ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) ) ) | 
						
							| 38 | 37 | adantr | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  =  ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) ) ) | 
						
							| 39 | 38 | adantr | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  =  ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) ) ) | 
						
							| 40 | 39 36 | difeq12d | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  ∖  (  L  ‘ 𝑋 ) )  =  ( ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) )  ∖  (  L  ‘ 𝑌 ) ) ) | 
						
							| 41 |  | difundir | ⊢ ( ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  ∖  (  L  ‘ 𝑋 ) )  =  ( ( (  L  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) )  ∪  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) ) | 
						
							| 42 |  | difid | ⊢ ( (  L  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) )  =  ∅ | 
						
							| 43 | 42 | uneq1i | ⊢ ( ( (  L  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) )  ∪  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) )  =  ( ∅  ∪  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) ) | 
						
							| 44 |  | 0un | ⊢ ( ∅  ∪  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) )  =  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) | 
						
							| 45 | 41 43 44 | 3eqtri | ⊢ ( ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  ∖  (  L  ‘ 𝑋 ) )  =  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) ) | 
						
							| 46 |  | incom | ⊢ ( (  L  ‘ 𝑋 )  ∩  (  R  ‘ 𝑋 ) )  =  ( (  R  ‘ 𝑋 )  ∩  (  L  ‘ 𝑋 ) ) | 
						
							| 47 |  | lltropt | ⊢ (  L  ‘ 𝑋 )  <<s  (  R  ‘ 𝑋 ) | 
						
							| 48 |  | ssltdisj | ⊢ ( (  L  ‘ 𝑋 )  <<s  (  R  ‘ 𝑋 )  →  ( (  L  ‘ 𝑋 )  ∩  (  R  ‘ 𝑋 ) )  =  ∅ ) | 
						
							| 49 | 47 48 | mp1i | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  ∩  (  R  ‘ 𝑋 ) )  =  ∅ ) | 
						
							| 50 | 46 49 | eqtr3id | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  R  ‘ 𝑋 )  ∩  (  L  ‘ 𝑋 ) )  =  ∅ ) | 
						
							| 51 |  | disjdif2 | ⊢ ( ( (  R  ‘ 𝑋 )  ∩  (  L  ‘ 𝑋 ) )  =  ∅  →  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) )  =  (  R  ‘ 𝑋 ) ) | 
						
							| 52 | 50 51 | syl | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  R  ‘ 𝑋 )  ∖  (  L  ‘ 𝑋 ) )  =  (  R  ‘ 𝑋 ) ) | 
						
							| 53 | 45 52 | eqtrid | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( ( (  L  ‘ 𝑋 )  ∪  (  R  ‘ 𝑋 ) )  ∖  (  L  ‘ 𝑋 ) )  =  (  R  ‘ 𝑋 ) ) | 
						
							| 54 |  | difundir | ⊢ ( ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) )  ∖  (  L  ‘ 𝑌 ) )  =  ( ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) )  ∪  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) ) | 
						
							| 55 |  | difid | ⊢ ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) )  =  ∅ | 
						
							| 56 | 55 | uneq1i | ⊢ ( ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) )  ∪  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) )  =  ( ∅  ∪  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) ) | 
						
							| 57 |  | 0un | ⊢ ( ∅  ∪  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) )  =  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) | 
						
							| 58 | 54 56 57 | 3eqtri | ⊢ ( ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) )  ∖  (  L  ‘ 𝑌 ) )  =  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) ) | 
						
							| 59 |  | incom | ⊢ ( (  L  ‘ 𝑌 )  ∩  (  R  ‘ 𝑌 ) )  =  ( (  R  ‘ 𝑌 )  ∩  (  L  ‘ 𝑌 ) ) | 
						
							| 60 |  | lltropt | ⊢ (  L  ‘ 𝑌 )  <<s  (  R  ‘ 𝑌 ) | 
						
							| 61 |  | ssltdisj | ⊢ ( (  L  ‘ 𝑌 )  <<s  (  R  ‘ 𝑌 )  →  ( (  L  ‘ 𝑌 )  ∩  (  R  ‘ 𝑌 ) )  =  ∅ ) | 
						
							| 62 | 60 61 | mp1i | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑌 )  ∩  (  R  ‘ 𝑌 ) )  =  ∅ ) | 
						
							| 63 | 59 62 | eqtr3id | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  R  ‘ 𝑌 )  ∩  (  L  ‘ 𝑌 ) )  =  ∅ ) | 
						
							| 64 |  | disjdif2 | ⊢ ( ( (  R  ‘ 𝑌 )  ∩  (  L  ‘ 𝑌 ) )  =  ∅  →  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) )  =  (  R  ‘ 𝑌 ) ) | 
						
							| 65 | 63 64 | syl | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  R  ‘ 𝑌 )  ∖  (  L  ‘ 𝑌 ) )  =  (  R  ‘ 𝑌 ) ) | 
						
							| 66 | 58 65 | eqtrid | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( ( (  L  ‘ 𝑌 )  ∪  (  R  ‘ 𝑌 ) )  ∖  (  L  ‘ 𝑌 ) )  =  (  R  ‘ 𝑌 ) ) | 
						
							| 67 | 40 53 66 | 3eqtr3d | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  (  R  ‘ 𝑋 )  =  (  R  ‘ 𝑌 ) ) | 
						
							| 68 | 36 67 | oveq12d | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  |s  (  R  ‘ 𝑋 ) )  =  ( (  L  ‘ 𝑌 )  |s  (  R  ‘ 𝑌 ) ) ) | 
						
							| 69 |  | simpll1 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  𝑋  ∈   No  ) | 
						
							| 70 |  | lrcut | ⊢ ( 𝑋  ∈   No   →  ( (  L  ‘ 𝑋 )  |s  (  R  ‘ 𝑋 ) )  =  𝑋 ) | 
						
							| 71 | 69 70 | syl | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  |s  (  R  ‘ 𝑋 ) )  =  𝑋 ) | 
						
							| 72 |  | simpll2 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  𝑌  ∈   No  ) | 
						
							| 73 |  | lrcut | ⊢ ( 𝑌  ∈   No   →  ( (  L  ‘ 𝑌 )  |s  (  R  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 74 | 72 73 | syl | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑌 )  |s  (  R  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 75 | 68 71 74 | 3eqtr3d | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  ∧  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) )  →  𝑋  =  𝑌 ) | 
						
							| 76 | 35 75 | mtand | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  ¬  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) ) | 
						
							| 77 |  | dfpss2 | ⊢ ( (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 )  ↔  ( (  L  ‘ 𝑋 )  ⊆  (  L  ‘ 𝑌 )  ∧  ¬  (  L  ‘ 𝑋 )  =  (  L  ‘ 𝑌 ) ) ) | 
						
							| 78 | 28 76 77 | sylanbrc | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  𝑋  <s  𝑌 )  →  (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 ) ) | 
						
							| 79 | 78 | ex | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( 𝑋  <s  𝑌  →  (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 ) ) ) | 
						
							| 80 |  | dfpss3 | ⊢ ( (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 )  ↔  ( (  L  ‘ 𝑋 )  ⊆  (  L  ‘ 𝑌 )  ∧  ¬  (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 ) ) ) | 
						
							| 81 |  | ssdif0 | ⊢ ( (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 )  ↔  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  =  ∅ ) | 
						
							| 82 | 81 | necon3bbii | ⊢ ( ¬  (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 )  ↔  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  ≠  ∅ ) | 
						
							| 83 |  | n0 | ⊢ ( ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  ≠  ∅  ↔  ∃ 𝑥 𝑥  ∈  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) ) ) | 
						
							| 84 | 82 83 | bitri | ⊢ ( ¬  (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 )  ↔  ∃ 𝑥 𝑥  ∈  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) ) ) | 
						
							| 85 |  | eldif | ⊢ ( 𝑥  ∈  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  ↔  ( 𝑥  ∈  (  L  ‘ 𝑌 )  ∧  ¬  𝑥  ∈  (  L  ‘ 𝑋 ) ) ) | 
						
							| 86 | 22 | a1i | ⊢ ( 𝑌  ∈   No   →  (  L  ‘ 𝑌 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 } ) | 
						
							| 87 | 86 | eleq2d | ⊢ ( 𝑌  ∈   No   →  ( 𝑥  ∈  (  L  ‘ 𝑌 )  ↔  𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∣  𝑥  <s  𝑌 } ) ) | 
						
							| 88 | 87 25 | bitrdi | ⊢ ( 𝑌  ∈   No   →  ( 𝑥  ∈  (  L  ‘ 𝑌 )  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) ) ) | 
						
							| 89 | 17 | a1i | ⊢ ( 𝑋  ∈   No   →  (  L  ‘ 𝑋 )  =  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 } ) | 
						
							| 90 | 89 | eleq2d | ⊢ ( 𝑋  ∈   No   →  ( 𝑥  ∈  (  L  ‘ 𝑋 )  ↔  𝑥  ∈  { 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∣  𝑥  <s  𝑋 } ) ) | 
						
							| 91 | 90 20 | bitrdi | ⊢ ( 𝑋  ∈   No   →  ( 𝑥  ∈  (  L  ‘ 𝑋 )  ↔  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 ) ) ) | 
						
							| 92 | 91 | notbid | ⊢ ( 𝑋  ∈   No   →  ( ¬  𝑥  ∈  (  L  ‘ 𝑋 )  ↔  ¬  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 ) ) ) | 
						
							| 93 |  | ianor | ⊢ ( ¬  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∧  𝑥  <s  𝑋 )  ↔  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 ) ) | 
						
							| 94 | 92 93 | bitrdi | ⊢ ( 𝑋  ∈   No   →  ( ¬  𝑥  ∈  (  L  ‘ 𝑋 )  ↔  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 ) ) ) | 
						
							| 95 | 88 94 | bi2anan9r | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No  )  →  ( ( 𝑥  ∈  (  L  ‘ 𝑌 )  ∧  ¬  𝑥  ∈  (  L  ‘ 𝑋 ) )  ↔  ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 )  ∧  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 ) ) ) ) | 
						
							| 96 | 95 | 3adant3 | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ( 𝑥  ∈  (  L  ‘ 𝑌 )  ∧  ¬  𝑥  ∈  (  L  ‘ 𝑋 ) )  ↔  ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 )  ∧  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 ) ) ) ) | 
						
							| 97 |  | simprl | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) | 
						
							| 98 |  | simpl3 | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) ) | 
						
							| 99 | 98 | fveq2d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  (  O  ‘ (  bday  ‘ 𝑋 ) )  =  (  O  ‘ (  bday  ‘ 𝑌 ) ) ) | 
						
							| 100 | 97 99 | eleqtrrd | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) ) ) | 
						
							| 101 | 100 | pm2.24d | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 102 |  | simpll1 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑋  ∈   No  ) | 
						
							| 103 |  | oldssno | ⊢ (  O  ‘ (  bday  ‘ 𝑌 ) )  ⊆   No | 
						
							| 104 | 103 97 | sselid | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  𝑥  ∈   No  ) | 
						
							| 105 | 104 | adantr | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑥  ∈   No  ) | 
						
							| 106 |  | simpll2 | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑌  ∈   No  ) | 
						
							| 107 |  | simpl1 | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  𝑋  ∈   No  ) | 
						
							| 108 |  | slenlt | ⊢ ( ( 𝑋  ∈   No   ∧  𝑥  ∈   No  )  →  ( 𝑋  ≤s  𝑥  ↔  ¬  𝑥  <s  𝑋 ) ) | 
						
							| 109 | 107 104 108 | syl2anc | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  ( 𝑋  ≤s  𝑥  ↔  ¬  𝑥  <s  𝑋 ) ) | 
						
							| 110 | 109 | biimpar | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑋  ≤s  𝑥 ) | 
						
							| 111 |  | simplrr | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑥  <s  𝑌 ) | 
						
							| 112 | 102 105 106 110 111 | slelttrd | ⊢ ( ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  ∧  ¬  𝑥  <s  𝑋 )  →  𝑋  <s  𝑌 ) | 
						
							| 113 | 112 | ex | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  ( ¬  𝑥  <s  𝑋  →  𝑋  <s  𝑌 ) ) | 
						
							| 114 | 101 113 | jaod | ⊢ ( ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  ∧  ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 ) )  →  ( ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 )  →  𝑋  <s  𝑌 ) ) | 
						
							| 115 | 114 | expimpd | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ( ( 𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑌 ) )  ∧  𝑥  <s  𝑌 )  ∧  ( ¬  𝑥  ∈  (  O  ‘ (  bday  ‘ 𝑋 ) )  ∨  ¬  𝑥  <s  𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 116 | 96 115 | sylbid | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ( 𝑥  ∈  (  L  ‘ 𝑌 )  ∧  ¬  𝑥  ∈  (  L  ‘ 𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 117 | 85 116 | biimtrid | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( 𝑥  ∈  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 118 | 117 | exlimdv | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ∃ 𝑥 𝑥  ∈  ( (  L  ‘ 𝑌 )  ∖  (  L  ‘ 𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 119 | 84 118 | biimtrid | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ¬  (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 )  →  𝑋  <s  𝑌 ) ) | 
						
							| 120 | 119 | adantld | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( ( (  L  ‘ 𝑋 )  ⊆  (  L  ‘ 𝑌 )  ∧  ¬  (  L  ‘ 𝑌 )  ⊆  (  L  ‘ 𝑋 ) )  →  𝑋  <s  𝑌 ) ) | 
						
							| 121 | 80 120 | biimtrid | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 )  →  𝑋  <s  𝑌 ) ) | 
						
							| 122 | 79 121 | impbid | ⊢ ( ( 𝑋  ∈   No   ∧  𝑌  ∈   No   ∧  (  bday  ‘ 𝑋 )  =  (  bday  ‘ 𝑌 ) )  →  ( 𝑋  <s  𝑌  ↔  (  L  ‘ 𝑋 )  ⊊  (  L  ‘ 𝑌 ) ) ) |