#!/bin/python3

import sys
import math

def countArray(n, k, x):
    n -= x
    return int(math.factorial(k)/(math.factorial(n)*math.factorial(k-n)))
    

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)