2 | 20. f@0: L[c@0]  R[c] 21. increasing(f@0;L[c@0]) 22. s: L[c@0] List. ||s|| = k  ( x,y: ||s||. x < y  s[x] < s[y])  G(map(f;map(f@0;s))) = c@0 23. c@0 ||L|| 24. c@0 = c 25. f1: L[c@0]  n (increasing(f1;L[c@0]) & ( s: L[c@0] List. ||s|| = k  ( x,y: ||s||. x < y  s[x] < s[y])  G(map(f1;s)) = c@0)) Prop | 2 steps |