#include <bits/stdc++.h>
using namespace std;
const int N = 3e3 + 1;
typedef long long ll;
int h, w;
ll d[N][N], f[N][N];
ll base = 1e9 + 7;
ll p(int n, int m)
{
if (n*m == 0) return 1;
if (d[n][m] != -1) return d[n][m];
ll res = 0;
res = (res + 4*m*p(n - 1, m - 1)) % base;
res = (res + p(n - 1, m)) % base;
if (m >= 2) res = (res + m*(m - 1)/2*p(n - 1, m - 2)) % base;
if (n >= 2) res = (res + (n - 1)*m*p(n - 2, m - 1)) % base;
d[n][m] = res;
return res;
}
int main()
{
cin >> h >> w;
memset(d, -1, sizeof(d));
//memset(f, -1, sizeof(f));
//cout << p(h, w) <<' ' << p1(h, w) << endl;
cout << p(h, w) - 1;
}
