#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 3000;
const int MOD = 1e9 + 7;
ll dp[N + 10][N + 10];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
int n, m;
cin >> n >> m;
for(int i = 0; i <= n; i++) dp[i][0] = 1;
for(int j = 0; 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 - 1][j];
dp[i][j] += 4 * j * dp[i - 1][j - 1] % MOD;
if(j > 1) dp[i][j] += j * (j - 1) / 2 * dp[i - 1][j - 2] % MOD;
if(i > 1) dp[i][j] += (i - 1) * j * dp[i - 2][j - 1] % MOD;
dp[i][j] %= MOD;
}
}
cout << (dp[n][m] - 1 + MOD) % MOD;
}
