YES (VAR x y z) (RULES f(x,i(x)) -> e() f(x,f(i(x),y)) -> y f(i(x),x) -> e() h(i(x)) -> i(h(x)) i(f(x,y)) -> f(i(y),i(x)) f(i(x),f(x,y)) -> y h(e()) -> e() i(e()) -> e() i(i(x)) -> x f(e(),x) -> x f(f(x,y),z) -> f(x,f(y,z)) f(x,e()) -> x h(f(x,y)) -> f(h(x),h(y)) )