0 QTRS
minus(x, 0) → x minus(s(x), s(y)) → minus(x, y) quot(0, s(y)) → 0 quot(s(x), s(y)) → s(quot(minus(x, y), s(y))) plus(0, y) → y plus(s(x), y) → s(plus(x, y)) minus(minus(x, y), z) → minus(x, plus(y, z))