theorem
  for m,n being odd Element of NAT st m <= n & n <= len W & W.m = W.n
  holds for x being Element of NAT st m <= x & x <= len W.remove(m,n) holds W
.remove(m,n).x = W.(x - m + n) & x - m + n is Element of NAT & x - m + n <= len
  W by Lm30;
