#!/bin/python3

import sys
import math

import math

def nCr(n,r):
    f = math.factorial
    return f(n) / f(r) / f(n-r)

def countArray(n, k, x):
    # Return the number of ways to fill in the array.
    return int((nCr(k,n-2)))

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)