// vaziat meshki-ghermeze !
#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'
using namespace std;
typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;
const ll Mod = 1000000007LL;
const int N = 3e3 + 10;
const ll Inf = 2242545357980376863LL;
const ll Log = 30;
ll mul(ll a, ll b){
return (a * b) % Mod;
}
ll dp[N][N];
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
fill(dp[0], dp[0] + N, 1);
for(int i = 1; i < N; i++){
dp[i][0] = 1;
for(int j = 1; j < N; j++){
dp[i][j] = dp[i - 1][j];
dp[i][j] += mul(dp[i - 1][j - 1], mul(j, 4));
if(i >= 2)
dp[i][j] += mul(dp[i - 2][j - 1], mul(j, (i - 1)));
if(j >= 2)
dp[i][j] += mul(dp[i - 1][j - 2], 1ll * j * (j - 1) / 2ll);
dp[i][j] %= Mod;
}
}
debug(dp[1][1]);
ll W, H;
cin >> W >> H;
cout << dp[W][H]-1 << '\n';
return 0;
}
