#!/bin/python3

import sys
import math

def countArray(n, k, x):
    # Return the number of ways to fill in the array.
    r = math.factorial(n-2)

    h = math.factorial(k)
    z = math.factorial(k-(n-2))

    if n-2 == k:
        d = h
    else:
        d = int((h)/(r*z))
    return d

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)