/*  This Code is Submitted by wywcgs for Problem 1061 on 2005-10-29 at 11:11:53 */ 
#include <cstdio>

const int MAX = 32;

int main()
{
	long long e[MAX][MAX] = {0};
	int i, j, n, m;
	
	for(i = 0; i < MAX; i++) {
		e[i][i] = 1;
	}
	for(i = 1; i < MAX; i++) {
		for(j = 1; j < i; j++) {
			e[i][j] += e[i-1][j]*j + e[i-1][j-1];
		}
	}
	while(scanf("%d %d", &n, &m) == 2) {
		printf("%lld\n", e[n][m]);
	}
	
	return 0;
}