#include <bits/stdc++.h>
using namespace std;
long long dp[3001][3001];
bool visited[3001][3001];
long long MOD = 1e9 + 7;
long long f(int n, int m) {
if (n < 0 || m < 0) return 0;
if (n == 0 || m == 0) return 1;
if (visited[n][m]) return dp[n][m];
visited[n][m] = 1;
return dp[n][m] = (f(n - 1, m) + 4 * m * f(n - 1, m - 1) + f(n - 1, m - 2) * m * (m - 1) / 2 + f(n - 2, m - 1) * m * (n - 1)) % MOD;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, m;
cin >> n >> m;
cout << (f(n, m) - 1 + MOD) % MOD << endl;
return 0;
}
