#include <bits/stdc++.h>
using namespace std;
const int md = 1e9+7;
const int maxn = 3e3+5;
int dp[maxn][maxn];
void add(int &a, int b)
{
a += b;
if(a>= md) a-= md;
}
int mul(int a, int b)
{
return (1LL*a*b)%md;
}
int solve(int n, int m)
{
if(n == 0 || m == 0) return 1;
if(dp[n][m] != -1) return dp[n][m];
int &res = dp[n][m];
res = 0;
add(res, mul(4*m, solve(n-1, m-1)));
if(n>= 2) add(res, mul(m*(n-1), solve(n-2, m-1)));
if(m>= 2) add(res, mul(m*(m-1)/2, solve(n-1, m-2)));
add(res, solve(n-1, m));
return res;
}
int main()
{
int n, m; cin >> n >> m;
memset(dp, -1, sizeof dp);
cout << solve(n, m)-1 << endl;
}
