#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9 + 7;
int r, c;
int f[3005][3005];
int dp(int i, int j)
{
if (i <= 0 || j <= 0) return 1;
if (f[i][j] != -1) return f[i][j];
f[i][j] = 0;
f[i][j] = (f[i][j] + (dp(i - 1, j - 2) * (j * (j - 1)) / 2) % mod + (dp(i - 2, j - 1) * (i - 1) * j) % mod + (dp(i - 1, j) % mod) + (dp(i - 1, j - 1) * j * 4) % mod) % mod;
return f[i][j];
}
signed main()
{
cin >> r >> c;
memset(f, -1, sizeof(f));
cout << dp(r, c) - 1;
return 0;
}
