#include <bits/stdc++.h>
using namespace std;
const int64_t mod = 1000000007;
int64_t dp[3001][3001];
int64_t f(int64_t row, int64_t col){
if(row < 0 || col < 0)
return 0;
if(row == 0 || col == 0) return 1;
if(dp[row][col] != -1)
return dp[row][col];
int64_t val = f(row, col-1);
(val += row*4*f(row-1, col-1)) %= mod;
(val += row*(col-1)*f(row-1, col-2)) %= mod;
(val += row*(row-1)/2*f(row-2, col-1)) %= mod;
return dp[row][col] = val;
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int h, w;
cin >> h >> w;
memset(dp, -1, sizeof dp);
cout << (f(h, w) - 1 + mod) % mod << '\n';
return 0;
}
