MAYBE

Problem:
 minus(x,y) -> cond(equal(min(x,y),y),x,y)
 cond(true(),x,y) -> s(minus(x,s(y)))
 min(0(),v) -> 0()
 min(u,0()) -> 0()
 min(s(u),s(v)) -> s(min(u,v))
 equal(0(),0()) -> true()
 equal(s(x),0()) -> false()
 equal(0(),s(y)) -> false()
 equal(s(x),s(y)) -> equal(x,y)

Proof:
 Open