MAYBE

Problem:
 -(x,0()) -> x
 -(s(x),s(y)) -> -(x,y)
 +(0(),y) -> y
 +(s(x),y) -> s(+(x,y))
 *(x,0()) -> 0()
 *(x,s(y)) -> +(x,*(x,y))
 f(s(x),y) -> f(-(*(s(x),s(y)),s(*(s(x),y))),*(y,y))

Proof:
 DP Processor:
  DPs:
   -#(s(x),s(y)) -> -#(x,y)
   +#(s(x),y) -> +#(x,y)
   *#(x,s(y)) -> *#(x,y)
   *#(x,s(y)) -> +#(x,*(x,y))
   f#(s(x),y) -> *#(y,y)
   f#(s(x),y) -> *#(s(x),y)
   f#(s(x),y) -> *#(s(x),s(y))
   f#(s(x),y) -> -#(*(s(x),s(y)),s(*(s(x),y)))
   f#(s(x),y) -> f#(-(*(s(x),s(y)),s(*(s(x),y))),*(y,y))
  TRS:
   -(x,0()) -> x
   -(s(x),s(y)) -> -(x,y)
   +(0(),y) -> y
   +(s(x),y) -> s(+(x,y))
   *(x,0()) -> 0()
   *(x,s(y)) -> +(x,*(x,y))
   f(s(x),y) -> f(-(*(s(x),s(y)),s(*(s(x),y))),*(y,y))
  Usable Rule Processor:
   DPs:
    -#(s(x),s(y)) -> -#(x,y)
    +#(s(x),y) -> +#(x,y)
    *#(x,s(y)) -> *#(x,y)
    *#(x,s(y)) -> +#(x,*(x,y))
    f#(s(x),y) -> *#(y,y)
    f#(s(x),y) -> *#(s(x),y)
    f#(s(x),y) -> *#(s(x),s(y))
    f#(s(x),y) -> -#(*(s(x),s(y)),s(*(s(x),y)))
    f#(s(x),y) -> f#(-(*(s(x),s(y)),s(*(s(x),y))),*(y,y))
   TRS:
    *(x,0()) -> 0()
    *(x,s(y)) -> +(x,*(x,y))
    +(0(),y) -> y
    +(s(x),y) -> s(+(x,y))
    -(s(x),s(y)) -> -(x,y)
    -(x,0()) -> x
   Open