#include <bits/stdc++.h>
using namespace std;
const int maxn = 3005;
const int mod = 1e9 + 7;
int n, m;
long long f(int rows, int cols)
{
if (rows < 0 || cols < 0)
{
return 0;
}
if (rows == 0 || cols == 0)
{
return 1;
}
long long ans = 0;
ans += f(rows - 1, cols);
ans %= mod;
ans += (4LL * cols) * f(rows - 1, cols - 1);
ans %= mod;
ans += ((1LL * cols) * (1LL * cols - 1LL) / 2LL) * f(rows - 1, cols - 2);
ans %= mod;
ans += (1LL * cols) * (1LL * (rows - 1)) * f(rows - 2, cols - 1);
ans %= mod;
return ans;
}
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int main()
{
fastIO();
cin >> n >> m;
cout << f(n, m) - 1 << endl;
return 0;
}
