text: def lots_of_pie(n,k):
      if n < 0 or k < 0 or n < k:
          return "-1"
      from functools import reduce
      g = lambda x, y: x*y
      #return reduce(g, range(n, n-k, -1)) // reduce(g, range(2, k+1))
      return str(reduce(g, range(n, n-k, -1)) // reduce(g, range(2, k+1)))
  