| Step | Hyp | Ref | Expression | 
						
							| 1 |  | efgval.w |  |-  W = ( _I ` Word ( I X. 2o ) ) | 
						
							| 2 |  | efgval.r |  |-  .~ = ( ~FG ` I ) | 
						
							| 3 |  | efgval2.m |  |-  M = ( y e. I , z e. 2o |-> <. y , ( 1o \ z ) >. ) | 
						
							| 4 |  | efgval2.t |  |-  T = ( v e. W |-> ( n e. ( 0 ... ( # ` v ) ) , w e. ( I X. 2o ) |-> ( v splice <. n , n , <" w ( M ` w ) "> >. ) ) ) | 
						
							| 5 |  | efgred.d |  |-  D = ( W \ U_ x e. W ran ( T ` x ) ) | 
						
							| 6 |  | efgred.s |  |-  S = ( m e. { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } |-> ( m ` ( ( # ` m ) - 1 ) ) ) | 
						
							| 7 |  | efgredlem.1 |  |-  ( ph -> A. a e. dom S A. b e. dom S ( ( # ` ( S ` a ) ) < ( # ` ( S ` A ) ) -> ( ( S ` a ) = ( S ` b ) -> ( a ` 0 ) = ( b ` 0 ) ) ) ) | 
						
							| 8 |  | efgredlem.2 |  |-  ( ph -> A e. dom S ) | 
						
							| 9 |  | efgredlem.3 |  |-  ( ph -> B e. dom S ) | 
						
							| 10 |  | efgredlem.4 |  |-  ( ph -> ( S ` A ) = ( S ` B ) ) | 
						
							| 11 |  | efgredlem.5 |  |-  ( ph -> -. ( A ` 0 ) = ( B ` 0 ) ) | 
						
							| 12 |  | efgredlemb.k |  |-  K = ( ( ( # ` A ) - 1 ) - 1 ) | 
						
							| 13 |  | efgredlemb.l |  |-  L = ( ( ( # ` B ) - 1 ) - 1 ) | 
						
							| 14 | 1 2 3 4 5 6 | efgsdm |  |-  ( A e. dom S <-> ( A e. ( Word W \ { (/) } ) /\ ( A ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` A ) ) ( A ` i ) e. ran ( T ` ( A ` ( i - 1 ) ) ) ) ) | 
						
							| 15 | 14 | simp1bi |  |-  ( A e. dom S -> A e. ( Word W \ { (/) } ) ) | 
						
							| 16 | 8 15 | syl |  |-  ( ph -> A e. ( Word W \ { (/) } ) ) | 
						
							| 17 | 16 | eldifad |  |-  ( ph -> A e. Word W ) | 
						
							| 18 |  | wrdf |  |-  ( A e. Word W -> A : ( 0 ..^ ( # ` A ) ) --> W ) | 
						
							| 19 | 17 18 | syl |  |-  ( ph -> A : ( 0 ..^ ( # ` A ) ) --> W ) | 
						
							| 20 |  | fzossfz |  |-  ( 0 ..^ ( ( # ` A ) - 1 ) ) C_ ( 0 ... ( ( # ` A ) - 1 ) ) | 
						
							| 21 |  | lencl |  |-  ( A e. Word W -> ( # ` A ) e. NN0 ) | 
						
							| 22 | 17 21 | syl |  |-  ( ph -> ( # ` A ) e. NN0 ) | 
						
							| 23 | 22 | nn0zd |  |-  ( ph -> ( # ` A ) e. ZZ ) | 
						
							| 24 |  | fzoval |  |-  ( ( # ` A ) e. ZZ -> ( 0 ..^ ( # ` A ) ) = ( 0 ... ( ( # ` A ) - 1 ) ) ) | 
						
							| 25 | 23 24 | syl |  |-  ( ph -> ( 0 ..^ ( # ` A ) ) = ( 0 ... ( ( # ` A ) - 1 ) ) ) | 
						
							| 26 | 20 25 | sseqtrrid |  |-  ( ph -> ( 0 ..^ ( ( # ` A ) - 1 ) ) C_ ( 0 ..^ ( # ` A ) ) ) | 
						
							| 27 | 1 2 3 4 5 6 7 8 9 10 11 | efgredlema |  |-  ( ph -> ( ( ( # ` A ) - 1 ) e. NN /\ ( ( # ` B ) - 1 ) e. NN ) ) | 
						
							| 28 | 27 | simpld |  |-  ( ph -> ( ( # ` A ) - 1 ) e. NN ) | 
						
							| 29 |  | fzo0end |  |-  ( ( ( # ` A ) - 1 ) e. NN -> ( ( ( # ` A ) - 1 ) - 1 ) e. ( 0 ..^ ( ( # ` A ) - 1 ) ) ) | 
						
							| 30 | 28 29 | syl |  |-  ( ph -> ( ( ( # ` A ) - 1 ) - 1 ) e. ( 0 ..^ ( ( # ` A ) - 1 ) ) ) | 
						
							| 31 | 12 30 | eqeltrid |  |-  ( ph -> K e. ( 0 ..^ ( ( # ` A ) - 1 ) ) ) | 
						
							| 32 | 26 31 | sseldd |  |-  ( ph -> K e. ( 0 ..^ ( # ` A ) ) ) | 
						
							| 33 | 19 32 | ffvelcdmd |  |-  ( ph -> ( A ` K ) e. W ) | 
						
							| 34 | 1 2 3 4 5 6 | efgsdm |  |-  ( B e. dom S <-> ( B e. ( Word W \ { (/) } ) /\ ( B ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` B ) ) ( B ` i ) e. ran ( T ` ( B ` ( i - 1 ) ) ) ) ) | 
						
							| 35 | 34 | simp1bi |  |-  ( B e. dom S -> B e. ( Word W \ { (/) } ) ) | 
						
							| 36 | 9 35 | syl |  |-  ( ph -> B e. ( Word W \ { (/) } ) ) | 
						
							| 37 | 36 | eldifad |  |-  ( ph -> B e. Word W ) | 
						
							| 38 |  | wrdf |  |-  ( B e. Word W -> B : ( 0 ..^ ( # ` B ) ) --> W ) | 
						
							| 39 | 37 38 | syl |  |-  ( ph -> B : ( 0 ..^ ( # ` B ) ) --> W ) | 
						
							| 40 |  | fzossfz |  |-  ( 0 ..^ ( ( # ` B ) - 1 ) ) C_ ( 0 ... ( ( # ` B ) - 1 ) ) | 
						
							| 41 |  | lencl |  |-  ( B e. Word W -> ( # ` B ) e. NN0 ) | 
						
							| 42 | 37 41 | syl |  |-  ( ph -> ( # ` B ) e. NN0 ) | 
						
							| 43 | 42 | nn0zd |  |-  ( ph -> ( # ` B ) e. ZZ ) | 
						
							| 44 |  | fzoval |  |-  ( ( # ` B ) e. ZZ -> ( 0 ..^ ( # ` B ) ) = ( 0 ... ( ( # ` B ) - 1 ) ) ) | 
						
							| 45 | 43 44 | syl |  |-  ( ph -> ( 0 ..^ ( # ` B ) ) = ( 0 ... ( ( # ` B ) - 1 ) ) ) | 
						
							| 46 | 40 45 | sseqtrrid |  |-  ( ph -> ( 0 ..^ ( ( # ` B ) - 1 ) ) C_ ( 0 ..^ ( # ` B ) ) ) | 
						
							| 47 |  | fzo0end |  |-  ( ( ( # ` B ) - 1 ) e. NN -> ( ( ( # ` B ) - 1 ) - 1 ) e. ( 0 ..^ ( ( # ` B ) - 1 ) ) ) | 
						
							| 48 | 27 47 | simpl2im |  |-  ( ph -> ( ( ( # ` B ) - 1 ) - 1 ) e. ( 0 ..^ ( ( # ` B ) - 1 ) ) ) | 
						
							| 49 | 13 48 | eqeltrid |  |-  ( ph -> L e. ( 0 ..^ ( ( # ` B ) - 1 ) ) ) | 
						
							| 50 | 46 49 | sseldd |  |-  ( ph -> L e. ( 0 ..^ ( # ` B ) ) ) | 
						
							| 51 | 39 50 | ffvelcdmd |  |-  ( ph -> ( B ` L ) e. W ) | 
						
							| 52 | 33 51 | jca |  |-  ( ph -> ( ( A ` K ) e. W /\ ( B ` L ) e. W ) ) |