#include <bits/stdc++.h>
using namespace std;
void setup()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
const long long mod = 1e9 + 7;
int n, m;
long long f[5001][5001];
int main()
{
setup();
cin >> n >> m;
f[0][0] = 1;
for (int i = 0; i <= n; ++i)
{
for (int j = 0; j <= m; ++j)
{
if (i == 0 || j == 0)
{
f[i][j] = 1;
continue;
}
(f[i][j] = f[i][j - 1] + f[i - 1][j - 1] * i * 4) %= mod;
if (2 <= j)
{
(f[i][j] += f[i - 1][j - 2] * i * (j - 1)) %= mod;
}
if (2 <= i)
{
(f[i][j] += f[i - 2][j - 1] * i * (i - 1) / 2) %= mod;
}
}
}
cout << (f[n][m] - 1 + mod) % mod;
return 0;
}
