| Step | Hyp | Ref | Expression | 
						
							| 1 |  | nnon |  | 
						
							| 2 |  | onnbtwn |  | 
						
							| 3 | 1 2 | syl |  | 
						
							| 4 | 3 | 3ad2ant1 |  | 
						
							| 5 |  | suceq |  | 
						
							| 6 | 5 | eqeq1d |  | 
						
							| 7 | 6 | 3ad2ant3 |  | 
						
							| 8 |  | ovex |  | 
						
							| 9 | 8 | sucid |  | 
						
							| 10 |  | eleq2 |  | 
						
							| 11 | 9 10 | mpbii |  | 
						
							| 12 |  | 2onn |  | 
						
							| 13 |  | nnmord |  | 
						
							| 14 | 12 13 | mp3an3 |  | 
						
							| 15 |  | simpl |  | 
						
							| 16 | 14 15 | biimtrrdi |  | 
						
							| 17 | 11 16 | syl5 |  | 
						
							| 18 |  | simpr |  | 
						
							| 19 |  | nnmcl |  | 
						
							| 20 | 12 19 | mpan |  | 
						
							| 21 |  | nnon |  | 
						
							| 22 |  | oa1suc |  | 
						
							| 23 | 20 21 22 | 3syl |  | 
						
							| 24 |  | 1oex |  | 
						
							| 25 | 24 | sucid |  | 
						
							| 26 |  | df-2o |  | 
						
							| 27 | 25 26 | eleqtrri |  | 
						
							| 28 |  | 1onn |  | 
						
							| 29 |  | nnaord |  | 
						
							| 30 | 28 12 20 29 | mp3an12i |  | 
						
							| 31 | 27 30 | mpbii |  | 
						
							| 32 |  | nnmsuc |  | 
						
							| 33 | 12 32 | mpan |  | 
						
							| 34 | 31 33 | eleqtrrd |  | 
						
							| 35 | 23 34 | eqeltrrd |  | 
						
							| 36 | 35 | ad2antrr |  | 
						
							| 37 | 18 36 | eqeltrrd |  | 
						
							| 38 |  | peano2 |  | 
						
							| 39 |  | nnmord |  | 
						
							| 40 | 12 39 | mp3an3 |  | 
						
							| 41 | 38 40 | sylan2 |  | 
						
							| 42 | 41 | ancoms |  | 
						
							| 43 | 42 | adantr |  | 
						
							| 44 | 37 43 | mpbird |  | 
						
							| 45 | 44 | simpld |  | 
						
							| 46 | 45 | ex |  | 
						
							| 47 | 17 46 | jcad |  | 
						
							| 48 | 47 | 3adant3 |  | 
						
							| 49 | 7 48 | sylbid |  | 
						
							| 50 | 4 49 | mtod |  |