include <bits/stdc++.h>
using namespace std;
int dp[101][101],n,m;
int main(){
1653dp[0][0]1;
scanf("%d%d",&n,&m);
for (int i1;i<m;i++)
for (int j1;j<n;j++){
if (j>1) dp[i][j]+dp[i-1][j-1];
if (j>2) dp[i][j]+dp[i-1][j-2];
if (j>3) dp[i][j]+dp[i-1][j-3];
}
printf("%d\n",dp[m][n]);
}