#include <bits/stdc++.h>
using namespace std;
const long long maxn = 3e3 + 12, mod = 1e9 + 7, inf = 1e9 + 12 ;
long long n, m, dp[maxn][maxn];
int main(){
cin >> n >> m;
dp[0][0] = 1;
for(int i = 1; i <= n; i++)
dp[i][0] = 1;
for(int j = 1; j <= m; j++)
dp[0][j] = 1;
for(int i = 1; i <= n; i++)
for(int j = 1; j <= m; j++){
dp[i][j] += dp[i][j - 1];
dp[i][j] += i * dp[i - 1][j - 1] * 4;
if(j >= 2)
dp[i][j] += i * (j - 1) * dp[i - 1][j - 2];
if(i >= 2)
dp[i][j] += (i * (i - 1) / 2) * dp[i - 2][j - 1];
dp[i][j] %= mod;
// cout << i << ' ' << j << ' ' << dp[i][j] << endl;
}
cout << (dp[n][m] - 1 + mod * 2) % mod << endl;
}
