#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 3e5+5;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll n;
ll comb[10005];
ll dp[3005][3005];
ll do_it(ll satir, ll sutun){
if(dp[satir][sutun] != -1) return dp[satir][sutun];
if(sutun < 0 || satir < 0) return 0;
if(satir <= 0){
return 1;
}
ll ans = 0;
ans = (ans + comb[sutun]*do_it(satir - 1, sutun - 2)%mod)%mod;
ans = (ans + sutun*(satir - 1)%mod*do_it(satir - 2, sutun - 1)%mod)%mod;
ans = (ans + 4*sutun*do_it(satir - 1, sutun - 1)%mod)%mod;
ans = (ans + do_it(satir - 1, sutun))%mod;
return dp[satir][sutun] = ans;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
#ifdef Local
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
#endif
ll W, H;
cin>>W>>H;
memset(dp, -1, sizeof(dp));
for(int i = 2; i <= 1e4; i++){
comb[i] = i*(i - 1) / 2;
}
cout<< (do_it(H, W) - 1 + mod) % mod;
#ifdef Local
cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
#endif
}
