Input TRS:
    1: top(free(x)) -> top(check(new(x)))
    2: new(free(x)) -> free(new(x))
    3: old(free(x)) -> free(old(x))
    4: new(serve()) -> free(serve())
    5: old(serve()) -> free(serve())
    6: check(free(x)) -> free(check(x))
    7: check(new(x)) -> new(check(x))
    8: check(old(x)) -> old(check(x))
    9: check(old(x)) -> old(x)
Number of Rules: 9
Direct QWPOS(Sum) ... failed.