Input TRS:
    1: +(0(),y) -> y
    2: +(s(x),y) -> s(+(x,y))
    3: -(0(),y) -> 0()
    4: -(x,0()) -> x
    5: -(s(x),s(y)) -> -(x,y)
Number of Rules: 5
Direct POLO(Sum) ... failed.