#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int mod = 1e9 + 7;
ll dp[3005][3005];
ll DP(int i , int j){
if(i < 0 || j < 0) return 0;
if(i == 0 || j == 0) return 1;
ll &ret = dp[i][j];
if(ret != -1) return ret;
ret = 0;
ret += 4 * j * DP(i - 1 , j - 1) % mod;
ret %= mod;
ret += DP(i - 1 , j) % mod;
ret %= mod;
ret += (j * (j - 1))/2 * DP(i - 1 , j - 2) % mod;
ret %= mod;
ret += j * (i - 1) * DP(i - 2 , j - 1) % mod;
ret %= mod;
return ret;
}
int main (){
ios_base::sync_with_stdio(0); cin.tie(0);
int h , w;
cin >> h >> w;
memset(dp , -1 , sizeof(dp));
cout << (DP(h , w) + mod - 1) % mod;
return 0;
}
