#include <bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 5e3 + 5, mod = 1e9 + 7;
int dp[maxn][maxn];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
for(int i = 0; i <= n; i++) for(int j = 0; j <= m; j++) dp[i][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] += 4 * i * dp[i - 1][j - 1];
if(i >= 2) dp[i][j] += dp[i - 2][j - 1] * (i) * (i - 1) / 2;
if(j >= 2) dp[i][j] += dp[i - 1][j - 2] * (j - 1) * i;
dp[i][j] %= mod;
}
}
cout << (dp[n][m] - 1 + mod) % mod;
}
