MAYBE

Problem:
 foo(0(x1)) -> 0(s(p(p(p(s(s(s(p(s(x1))))))))))
 foo(s(x1)) -> p(s(p(p(p(s(s(p(s(s(p(s(foo(p(p(s(s(p(s(bar(p(p(s(s(p(s(x1))))))))))))))))))))))))))
 bar(0(x1)) -> 0(p(s(s(s(x1)))))
 bar(s(x1)) -> p(s(p(p(s(s(foo(s(p(p(s(s(x1))))))))))))
 p(p(s(x1))) -> p(x1)
 p(s(x1)) -> x1
 p(0(x1)) -> 0(s(s(s(s(x1)))))

Proof:
 Open