#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9 + 7;
signed main()
{
int n, m;
cin >> n >> m;
int dp[n + 1][m + 1];
for (int i = 0; i <= n; i++) for (int j = 0; j <= m; j++) dp[i][j] = !i || !j;
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
dp[i][j] += dp[i - 1][j];
dp[i][j] += dp[i - 1][j - 1] * j * 4;
if (j > 1) dp[i][j] += dp[i - 1][j - 2] * j * (j - 1) / 2;
if (i > 1) dp[i][j] += dp[i - 2][j - 1] * j * (i - 1);
dp[i][j] %= mod;
}
}
cout << (dp[n][m] + mod - 1) % mod << '\n';
}
