Problem:
 +(x,0()) -> x
 +(x,s(y)) -> s(+(x,y))
 +(x,p(y)) -> p(+(x,y))
 +(0(),y) -> y
 +(s(x),y) -> s(+(x,y))
 +(p(x),y) -> p(+(x,y))
 s(p(x)) -> x
 p(s(x)) -> x
 -(0()) -> 0()
 -(s(x)) -> p(-(x))
 -(p(x)) -> s(-(x))
 +(+(x,y),z) -> +(x,+(y,z))
 +(x,y) -> +(y,x)
 -(+(x,y)) -> +(-(x),-(y))

Proof:
 Open