code: def ncr(n, r):
      """
      Calculate the combination of n and r.
  
      :param n: n
      :type n: int
      :param r: r
      :type r :int
      :return: the combination of n and r as int
      """
      if r > n:
          return 0
      r = min(r, n - r)
      numer = reduce(op.mul, range(n, n - r, -1), 1)
      denom = reduce(op.mul, range(1, r + 1), 1)
      return numer // denom
  
imports: from __future__ import division
  import math
  import operator
  from functools import reduce
  from .pycm_interpret import *
  from .pycm_ci import kappa_SE_calc, CI_calc, SE_calc
  from .pycm_util import complement
label_desc: Use image node_id 16 for calling a global function with example usage: ncr(n, r) and returns: unknown, int