#include <iostream>
#include <vector>
using namespace std;
/**
* JOI 2017/2018 Spring Training Camp - Tents
* Dinamik dasturlash O(H*W)
*/
long long dp[3005][3005];
const int MOD = 1000000007;
int main() {
int H, W;
cin >> H >> W;
// Baza holati: 0 ta qator yoki 0 ta ustun bo'lsa, 1 ta usul (bo'sh holat)
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++) {
// 1. Birinchi qator bo'sh
dp[i][j] = dp[i-1][j];
// 2. Birinchi qatorda 1 ta chodir (4 yo'nalishdan biri)
dp[i][j] = (dp[i][j] + 4LL * j * dp[i-1][j-1]) % MOD;
// 3. Birinchi qatorda 2 ta chodir (Sharq-G'arb juftligi)
if (j >= 2) {
long long combinations = (1LL * j * (j - 1) / 2) % MOD;
dp[i][j] = (dp[i][j] + combinations * dp[i-1][j-2]) % MOD;
}
// 4. Birinchi qatordagi chodir boshqa bir qatordagi bilan juftlashgan (Shimol-Janub)
if (i >= 2) {
long long row_col_choices = (1LL * j * (i - 1)) % MOD;
dp[i][j] = (dp[i][j] + row_col_choices * dp[i-2][j-1]) % MOD;
}
}
}
// Natija: kamida bitta chodir bo'lishi kerak, shuning uchun bo'sh holatni (1) ayiramiz
long long result = (dp[H][W] - 1 + MOD) % MOD;
cout << result << endl;
return 0;
}
