#include <bits/stdc++.h>
using namespace std;
const int MAXN = 3005;
const int mod = 1e9 + 7;
typedef long long lint;
lint dp[MAXN][MAXN];
lint f(int x, int y){
if(y < 0 || x < 0) return 0;
if(x == 0) return 1;
if(~dp[x][y]) return dp[x][y];
lint ret = f(x-1, y);
ret += f(x-1, y-2) * (y * (y - 1) / 2);
ret += f(x-2, y-1) * y * (x - 1);
ret += f(x-1, y-1) * 4 * y;
return dp[x][y] = ret % mod;
}
int main(){
int n, m;
cin >> n >> m;
memset(dp, -1, sizeof(dp));
cout << (f(n, m) + mod - 1) % mod << endl;
}
