MAYBE

Problem:
 max(L(x)) -> x
 max(N(L(0()),L(y))) -> y
 max(N(L(s(x)),L(s(y)))) -> s(max(N(L(x),L(y))))
 max(N(L(x),N(y,z))) -> max(N(L(x),L(max(N(y,z)))))
 N(x,N(y,z)) -> N(N(x,y),z)
 N(N(x,y),z) -> N(x,N(y,z))
 N(x,y) -> N(y,x)

Proof:
 Open