numberOfRoutes :: Int -> Int -> Integer
numberOfRoutes m n = product [succ b .. a + b] `div` product [1 .. a]
    where a = fromIntegral (min m n)
          b = fromIntegral (max m n)
numberOfRoutes :: Int -> Int -> Integer
numberOfRoutes m n = product [succ b .. a + b] `div` product [1 .. a]
    where a = fromIntegral (min m n)
          b = fromIntegral (max m n)
numberOfRoutes m n = product [succ b .. a + b] `div` product [1 .. a]
    where a = fromIntegral (min m n)
          b = fromIntegral (max m n)