#!/bin/python3

import sys

def memoize(f):
    """ Memoization decorator for functions taking one or more arguments. """
    class memodict(dict):
        def __init__(self, f):
            self.f = f
        def __call__(self, *args):
            return self[args]
        def __missing__(self, key):
            ret = self[key] = self.f(*key)
            return ret
    return memodict(f)

@memoize
def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

def binomial(x, y):
    if (x,y) in bcache:
        return bcache[(x,y)]
    else:
        try:
            binom = factorial(x) // factorial(y) // factorial(x - y)
        except:
            binom = 0
        bcache[(x,y)] = binom
        return binom

def countArray(n, k, x):
    # Return the number of ways to fill in the array.
    return binomial(n, n-2)/(n-2)
    
    
if __name__ == "__main__":
    bcache = {}
    n, k, x = input().strip().split(' ')
    n, k, x = [int(n), int(k), int(x)]
    answer = countArray(n, k, x)
    print('%.f' % answer)