#!/bin/python3

import sys
from math import*
def countArray(n, k, x):
    # Return the number of ways to fill in the array.
    return factorial(k)//(factorial(k-n+2)*factorial(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)