(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))
)