#include<bits/stdc++.h>
using namespace std;
long long dp[3001][3001];
const int MOD = 1000000007;
int main() {
int H, W;
if (!(cin >> H >> W)) return 0;
for (int j = 0; j <= W; ++j) dp[0][j] = 1;
for (int i = 0; i <= H; ++i) dp[i][0] = 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] + 4LL * j % MOD * dp[i-1][j-1]) % MOD;
if (j >= 2) {
long long ways = 1LL * j * (j - 1) / 2 % MOD;
dp[i][j] = (dp[i][j] + ways * dp[i-1][j-2]) % MOD;
}
if (i >= 2) {
long long ways = 1LL * j * (i - 1) % MOD;
dp[i][j] = (dp[i][j] + ways * dp[i-2][j-1]) % MOD;
}
}
}
long long result = (dp[H][W] - 1 + MOD) % MOD;
cout << result << endl;
return 0;
}
// hello rahidil
