#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 3000 + 10;
const int mod = 1e9 + 7;
int dp[maxn][maxn];
int power(int a, int b){
if (b == 0)
return 1;
int ret = power(a, b / 2);
ret = 1ll * ret * ret % mod;
if (b & 1)
return 1ll * ret * a % mod;
return ret;
}
int main(){
ios_base::sync_with_stdio(false);
int n, m;
cin >> n >> m;
for (int i = 0; i <= max(n, m); i++)
dp[i][0] = dp[0][i] = 1;
int pw = power(2, mod - 2);
for (int i = 1; i <= n; i++){
for (int j = 1; j <= m; j++){
if (i == 1){
dp[i][j] = 4 * j + 1ll * j * (j - 1) % mod * pw % mod + 1;
dp[i][j] %= mod;
continue;
}
if (j == 1){
dp[i][j] = 4 * i + 1ll * i * (i - 1) % mod * pw % mod + 1;
dp[i][j] %= mod;
continue;
}
dp[i][j] = dp[i - 1][j];
dp[i][j] = (dp[i][j] + 4ll * dp[i - 1][j - 1] * j) % mod;
dp[i][j] = (dp[i][j] + 1ll * dp[i - 1][j - 2] * j % mod * (j - 1) % mod * pw % mod) % mod;
dp[i][j] = (dp[i][j] + 1ll * dp[i - 2][j - 1] * j % mod * (i - 1) % mod) % mod;
}
}
cout << (dp[n][m] - 1 + mod) % mod << endl;
}
