#!/bin/python

import sys
from itertools import izip

def ncr(n, r):
    r = min(r, n-r)
    if r == 0: return 1
    res = 1
    for k in range(1,r+1):
        res = res*(n-k+1)/k
    return res

def countArray(n, k, x):
    return ncr(k, n - 2)
    

if __name__ == "__main__":
    n, k, x = raw_input().strip().split(' ')
    n, k, x = [int(n), int(k), int(x)]
    answer = countArray(n, k, x)
    print answer