#include <bits/stdc++.h>
using namespace std;
const int kN = 3003;
const int MOD = 1e9 + 7;
int H, W;
int dp[kN][kN];
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
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) {
int64_t v = dp[i - 1][j];
v += 4ll * j * dp[i - 1][j - 1];
if (i >= 2) v += 1ll * dp[i - 2][j - 1] * (i - 1) * j;
if (j >= 2) v += 1ll * dp[i - 1][j - 2] * j * (j - 1) / 2;
dp[i][j] = v % MOD;
}
cout << (dp[H][W] + MOD - 1) % MOD << '\n';
return 0;
}
