| Step | Hyp | Ref
 | Expression | 
| 1 |   | peano2nc 6146 | 
. . . 4
       NC       
1c 
  NC   | 
| 2 |   | dflec2 6211 | 
. . . 4
        NC        1c    NC         c      1c         NC     
1c 
            | 
| 3 | 1, 2 | sylan2 460 | 
. . 3
        NC       NC         c     
1c 
 
     NC     
1c 
            | 
| 4 |   | nc0suc 6218 | 
. . . . 5
       NC        0c       
NC          1c    | 
| 5 |   | addceq2 4385 | 
. . . . . . . . . 10
       0c            
     0c   | 
| 6 |   | addcid1 4406 | 
. . . . . . . . . 10
       0c   
  | 
| 7 | 5, 6 | syl6eq 2401 | 
. . . . . . . . 9
       0c            
   | 
| 8 | 7 | eqeq2d 2364 | 
. . . . . . . 8
       0c         1c                  
1c 
      | 
| 9 |   | olc 373 | 
. . . . . . . . 9
            1c        c        
     1c    | 
| 10 | 9 | eqcoms 2356 | 
. . . . . . . 8
       
1c 
          c        
     1c    | 
| 11 | 8, 10 | syl6bi 219 | 
. . . . . . 7
       0c         1c                  c              1c     | 
| 12 | 11 | a1i 10 | 
. . . . . 6
        NC       NC          0c         1c                  c              1c      | 
| 13 |   | addceq2 4385 | 
. . . . . . . . . . . 12
            1c             
         
1c    | 
| 14 |   | addcass 4416 | 
. . . . . . . . . . . 12
             1c   
         
1c   | 
| 15 | 13, 14 | syl6eqr 2403 | 
. . . . . . . . . . 11
            1c             
           1c   | 
| 16 | 15 | eqeq2d 2364 | 
. . . . . . . . . 10
            1c          1c                  
1c 
     
       1c    | 
| 17 | 16 | biimpa 470 | 
. . . . . . . . 9
             1c         1c            
       1c               1c   | 
| 18 |   | simplr 731 | 
. . . . . . . . . . 11
         NC       NC         NC        
NC   | 
| 19 |   | ncaddccl 6145 | 
. . . . . . . . . . . 12
        NC       NC               NC   | 
| 20 | 19 | adantlr 695 | 
. . . . . . . . . . 11
         NC       NC         NC       
      
NC   | 
| 21 |   | peano4nc 6151 | 
. . . . . . . . . . 11
        NC          
  NC          
1c 
     
       1c                  | 
| 22 | 18, 20, 21 | syl2anc 642 | 
. . . . . . . . . 10
         NC       NC         NC          
1c 
     
       1c                  | 
| 23 |   | addlecncs 6210 | 
. . . . . . . . . . . . 13
        NC       NC        c          | 
| 24 | 23 | adantlr 695 | 
. . . . . . . . . . . 12
         NC       NC         NC        c          | 
| 25 |   | breq2 4644 | 
. . . . . . . . . . . 12
              
      c        c           | 
| 26 | 24, 25 | syl5ibrcom 213 | 
. . . . . . . . . . 11
         NC       NC         NC       
               c     | 
| 27 |   | orc 374 | 
. . . . . . . . . . 11
      c         c           
 
1c    | 
| 28 | 26, 27 | syl6 29 | 
. . . . . . . . . 10
         NC       NC         NC       
              
 c        
     1c     | 
| 29 | 22, 28 | sylbid 206 | 
. . . . . . . . 9
         NC       NC         NC          
1c 
     
       1c        c           
 
1c     | 
| 30 | 17, 29 | syl5 28 | 
. . . . . . . 8
         NC       NC         NC               
1c 
       1c                 
 c        
     1c     | 
| 31 | 30 | exp3a 425 | 
. . . . . . 7
         NC       NC         NC       
       1c         
1c 
              
 c        
     1c      | 
| 32 | 31 | rexlimdva 2739 | 
. . . . . 6
        NC       NC          
NC          1c          1c   
              c           
 
1c      | 
| 33 | 12, 32 | jaod 369 | 
. . . . 5
        NC       NC          
0c        NC         
1c        
 
1c 
              
 c        
     1c      | 
| 34 | 4, 33 | syl5 28 | 
. . . 4
        NC       NC          NC         1c                  c              1c      | 
| 35 | 34 | rexlimdv 2738 | 
. . 3
        NC       NC          
NC     
1c 
              
 c        
     1c     | 
| 36 | 3, 35 | sylbid 206 | 
. 2
        NC       NC         c     
1c 
      c           
 
1c     | 
| 37 |   | 1cnc 6140 | 
. . . . . 6
 
1c  
NC | 
| 38 |   | addlecncs 6210 | 
. . . . . 6
        NC   1c   NC        c      1c   | 
| 39 | 37, 38 | mpan2 652 | 
. . . . 5
       NC      c     
1c   | 
| 40 | 39 | adantl 452 | 
. . . 4
        NC       NC        c     
1c   | 
| 41 | 1 | adantl 452 | 
. . . . 5
        NC       NC          1c   
NC   | 
| 42 |   | lectr 6212 | 
. . . . 5
        NC       NC        1c    NC          c        c     
1c        c   
 
1c    | 
| 43 | 41, 42 | mpd3an3 1278 | 
. . . 4
        NC       NC          c        c     
1c        c   
 
1c    | 
| 44 | 40, 43 | mpan2d 655 | 
. . 3
        NC       NC         c        c     
1c    | 
| 45 |   | nclecid 6198 | 
. . . . . 6
       
1c 
  NC        1c   c   
 
1c   | 
| 46 | 1, 45 | syl 15 | 
. . . . 5
       NC       
1c 
 c      1c   | 
| 47 | 46 | adantl 452 | 
. . . 4
        NC       NC          1c   c     
1c   | 
| 48 |   | breq1 4643 | 
. . . 4
            1c        c      1c        
1c 
 c      1c    | 
| 49 | 47, 48 | syl5ibrcom 213 | 
. . 3
        NC       NC               1c       c     
1c    | 
| 50 | 44, 49 | jaod 369 | 
. 2
        NC       NC          c           
 
1c        c   
 
1c    | 
| 51 | 36, 50 | impbid 183 | 
1
        NC       NC         c     
1c 
 
    c             
1c     |