TIMEOUT
MAYBE
Trs:
 {               +(0(), y) -> y,
        +(minus(1()), 1()) -> 0(),
  +(minus(+(x, 1())), 1()) -> minus(x),
                 +(x, 0()) -> x,
             +(x, +(y, z)) -> +(+(x, y), z),
            +(x, minus(y)) -> minus(+(minus(x), y)),
                minus(0()) -> 0(),
           minus(minus(x)) -> x}
 Open