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 n being odd Element of NAT st n <= len W holds W.find(n) <= n &
  W.rfind(n) >= n by Lm49,Lm50;
