#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 3000;
const int MOD = 1e9+7;
ll dp[MAXN+1][MAXN+1];
ll n, m;
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
cin >> n >> m;
for (ll i = 0; i <= n; i++) {
for (ll j = 0; j <= m; j++) {
if (i == 0 || j == 0) {
dp[i][j] = 1;
continue;
}
ll m1 = j*(i-1);
m1 %= MOD;
ll m2 = j*(j-1)/2;
m2 %= MOD;
dp[i][j] += 4*j*dp[i-1][j-1];
dp[i][j] %= MOD;
dp[i][j] += dp[i-1][j];
dp[i][j] %= MOD;
if (j > 1) dp[i][j] += m2*dp[i-1][j-2];
dp[i][j] %= MOD;
if (i > 1) dp[i][j] += m1*dp[i-2][j-1];
dp[i][j] %= MOD;
}
}
cout << ((dp[n][m]-1+MOD)%MOD) << "\n";
}
