(VAR x y z )
(RULES 
        plus(x, 0) -> x
        plus(0, y) -> y
        plus(s(x), y) -> s(plus(x, y))
        times(0, y) -> 0
        times(s(0), y) -> y
        times(s(x), y) -> plus(y, times(x, y))
        div(0, y) -> 0
        div(x, y) -> quot(x, y, y)
        quot(0, s(y), z) -> 0
        quot(s(x), s(y), z) -> quot(x, y, z)
        quot(x, 0, s(z)) -> s(div(x, s(z)))
        div(div(x, y), z) -> div(x, times(y, z))
        
)