#include <stdio.h>

int factorial(int n) {
	int i, r;

	r = 1;
	for (i=1; i<=n; i++) {
		r *= i;
	}

	return r;
}

int main(void) {
	int n, r;

	scanf("%d", &n);
	scanf("%d", &r);
	
	printf("%d\n", factorial(n) / factorial(r) / factorial(n - r));

	return 0;
}