#include <iostream>
#include <fstream>
#include <ostream>
#include <istream>
#include <cmath>
#include <conio.h>
#include <stdio.h>
using namespace std;

int main(){
    ifstream in("input.txt");
    ofstream out("output.txt");

    int n, k;
    in >> n >> k;
    int m = (k - n) / 2;

    int s = 1; //это k!
    for (int i = 1; i <= k; i++) s *= i;

    int t = 1; //это (k-m)!
    for (int j = 1; j <= k - m; j++) t *= j;

    int p = 1; //это m!
    for (int l = 1; l <= m; l++) p *= l;

    out << s / (t * p);

    return 0;
}