#include <bits/stdc++.h>
using namespace std;
int n, m;
long long dp[3007][3007];
const long long mod = 1e9 + 7;
int main(){
ios_base::sync_with_stdio(0);
cin >> n >> m;
for(int i = 0; i <= m; i++) dp[0][i] = 1;
for(int i = 0; i <= n; i++) dp[i][0] = 1;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
dp[i][j] = (dp[i - 1][j] + 4LL * j * dp[i - 1][j - 1]) % mod;
if(i >= 2) dp[i][j] = (dp[i][j] + 1LL * (i - 1) * j * dp[i - 2][j - 1]) % mod;
if(j >= 2) dp[i][j] = (dp[i][j] + 1LL * j * (j - 1) / 2LL * dp[i - 1][j - 2]) % mod;
}
}
dp[n][m] = (dp[n][m] - 1 + mod) % mod;
cout << dp[n][m];
}
