(VAR x y )
(RULES 
        f(true,x) -> f(eq(0,minus(x,x)),plus1(x))
        plus1(x) -> plus(x,s(0))
        plus(0,y) -> y
        plus(s(x),y) -> s(plus(x,y))
        minus(x,0) -> x
        minus(0,y) -> 0
        minus(s(x),s(y)) -> minus(x,y)
        eq(0,0) -> true
        eq(s(x),0) -> false
        eq(0,s(y)) -> false
        eq(s(x),s(y)) -> eq(x,y)
        
)