interactTopMul :: [Xi] -> Xi -> [Pair Type]
interactTopMul [s,t] r
  | Just 1 <- mbZ = [ s === num 1, t === num 1 ]                        -- (s * t ~ 1)  => (s ~ 1, t ~ 1)
  | Just x <- mbX, Just z <- mbZ, Just y <- divide z x = [t === num y]  -- (3 * t ~ 15) => (t ~ 5)
  | Just y <- mbY, Just z <- mbZ, Just x <- divide z y = [s === num x]  -- (s * 3 ~ 15) => (s ~ 5)
  where
  mbX = isNumLitTy s
  mbY = isNumLitTy t
  mbZ = isNumLitTy r
interactTopMul :: [Xi] -> Xi -> [Pair Type]
interactTopMul [s,t] r
  | Just 1 <- mbZ = [ s === num 1, t === num 1 ]                        -- (s * t ~ 1)  => (s ~ 1, t ~ 1)
  | Just x <- mbX, Just z <- mbZ, Just y <- divide z x = [t === num y]  -- (3 * t ~ 15) => (t ~ 5)
  | Just y <- mbY, Just z <- mbZ, Just x <- divide z y = [s === num x]  -- (s * 3 ~ 15) => (s ~ 5)
  where
  mbX = isNumLitTy s
  mbY = isNumLitTy t
  mbZ = isNumLitTy r
interactTopMul [s,t] r
  | Just 1 <- mbZ = [ s === num 1, t === num 1 ]                        -- (s * t ~ 1)  => (s ~ 1, t ~ 1)
  | Just x <- mbX, Just z <- mbZ, Just y <- divide z x = [t === num y]  -- (3 * t ~ 15) => (t ~ 5)
  | Just y <- mbY, Just z <- mbZ, Just x <- divide z y = [s === num x]  -- (s * 3 ~ 15) => (s ~ 5)
  where
  mbX = isNumLitTy s
  mbY = isNumLitTy t
  mbZ = isNumLitTy r