#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ff first
#define ss second
#define pb push_back
template<class T, class U> inline bool chmin(T& a, const U& b) { if (a > b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmax(T& a, const U& b) { if (a < b) { a = b; return true; } return false; }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define rnd(l, r) uniform_int_distribution <int> (l, r)(rng)
const int inf = 1e6, mod = 1e9 + 7;
void solve(){
auto add = [&](int &a, int b) -> void{
a = (a + b) %mod;
if(a < 0) a += mod;
};
int h, w; cin >> h >> w;
vector <vector<int>> dp(h + 1, vector <int> (w + 1));
for ( int i = 0; i <= h; i++ ){
for ( int j = 0; j <= w; j++ ){
if ( !i || !j ){
dp[i][j] = 1;
continue;
}
add(dp[i][j], dp[i - 1][j - 1] * 4 * j + dp[i - 1][j]);
if ( i >= 2 ){
add(dp[i][j], dp[i - 2][j - 1] * (i - 1) * j);
}
if ( j >= 2 ){
add(dp[i][j], dp[i - 1][j - 2] * (j * (j - 1) / 2));
}
}
}
add(dp[h][w], -1);
cout << dp[h][w] << '\n';
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int tt = 1;
//cin >> tt;
while(tt--){
solve();
};
}
