MAYBE
Trs:
 {    gcd(0(), y) -> y,
  gcd(s(x), s(y)) -> if(<(x, y), gcd(s(x), -(y, x)), gcd(-(x, y), s(y))),
      gcd(x, 0()) -> x}
 Comment:
  We consider a duplicating trs.
  FAIL:
   Open