#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define all(x) x.begin(), x.end()
#define u_map unordered_map
const int maxn = 3e3 + 5, mod = 1e9 + 7;
ll dp[maxn][maxn];
ll c(int a) {
return (a * (a - 1) / 2) % mod;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, m;
cin >> n >> m;
for (int i = 0; i <= n; i++) {
dp[i][0] = 1;
}
for (int i = 0; i <= m; i++) {
dp[0][i] = 1;
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
dp[i][j] = dp[i][j - 1];
dp[i][j] = (dp[i][j] + (((i) * 4 % mod) * dp[i - 1][j - 1] % mod)) % mod;
dp[i][j] = (dp[i][j] + (((i) * (j - 1) % mod) * dp[i - 1][j - 2] % mod)) % mod;
dp[i][j] = (dp[i][j] + c(i) * dp[i - 2][j - 1] % mod) % mod;
}
}
cout << (dp[n][m] - 1 + mod) % mod;
return 0;
}
// dp[1][1] = 4;
// dp[2][1] = 9;
// dp[1][2] = 9;
// dp[1][3] = 15;
// dp[3][1] = 15;
// dp[2][3];
