% example53.sil %
while Nat < 0 do skip od;
while Pos <= 0 do skip od;
while (i - j >= 1) do
  while (i<>i0) | (j<>j0) | (Pos<>Pos0) | (Nat<>Nat0) do skip od;
  i := i - Nat;
  j := j - Pos
od;;