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