reserve G,G1,G2 for _Graph;
reserve W,W1,W2 for Walk of G;
reserve e,x,y,z for set;
reserve v for Vertex of G;
reserve n,m for Element of NAT;

theorem
  for m, n being odd Element of NAT st m <= n & n <= len W holds W.cut(m
,n).first() = W.m & W.cut(m,n).last() = W.n & W.cut(m,n) is_Walk_from W.m, W.n
  by Lm16;
