#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 3002;
const ll mod = 1e9 + 7;
ll dp[N][N];
ll multi(ll a, ll b){
return ((a % mod) * (b % mod)) % mod;
}
ll add(ll a, ll b){
return (a + b) % mod;
}
ll f(ll x, ll y){
if(x < 0 || y < 0) return 0;
if(x == 0 || y == 0) return 1;
auto &cur = dp[x][y];
if(cur != -1) return cur;
cur = add(
add(
add(
f(x - 1, y),
multi(4LL*y, f(x - 1, y - 1))
),
multi((y*(y - 1LL))/2LL, f(x - 1, y - 2))
),
multi(y*(x - 1LL), f(x - 2, y - 1))
);
return cur;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
memset(dp, -1, sizeof(dp));
int h, w; cin >> h >> w;
cout << (f(h, w) - 1LL + mod) % mod << '\n';
return 0;
}
