#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr int N = 3005;
constexpr int MOD = 1e9+7;
int h, w;
ll dp[N][N];
ll mul(ll a, ll b) {
return a * b % MOD;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
cin >> h >> w;
for (int i = 0; i <= max(h, w); ++i) {
dp[i][0] = dp[0][i] = 1;
}
for (int i = 1; i <= h; ++i) {
for (int j = 1; j <= w; ++j) {
if (j >= 2) dp[i][j] += mul(j * (j - 1) / 2, dp[i-1][j-2]);
dp[i][j] += mul(4 * j, dp[i-1][j-1]);
if (i >= 2) dp[i][j] += mul(j * (i - 1), dp[i-2][j-1]);
dp[i][j] += dp[i-1][j];
dp[i][j] %= MOD;
}
}
cout << (dp[h][w] - 1 + MOD) % MOD;
}
