#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <set>
#include <queue>
#include <algorithm>
#define MAXN 0x7fffffff
using namespace std;
long long a,b,c,d,f[50][50];
int main(void)
{
    freopen("k.in","r",stdin);
    freopen("k.out","w",stdout);
	scanf("%lld%lld",&a,&b);
	f[1][1]=1;
	for (c=2;c<=a;c++)
		for (d=1;d<=b;d++)
			f[c][d]=f[c-1][d]*d+f[c-1][d-1]*(c-d+1);
	printf("%lld",f[a][b]);
	fclose(stdin);
    fclose(stdout);
    return 0;
}