#!/bin/python3

import sys
import math

def countArray(n, k, x):
  r=n-2
  f = math.factorial
  return f(k) // (f(r)*f(k-r))
if __name__ == "__main__":
    n, k, x = input().strip().split(' ')
    n, k, x = [int(n), int(k), int(x)]
    answer = countArray(n, k, x)
    print(answer)