#include<bits/stdc++.h>
#define int long long
using namespace std;
int dp[3005][3005];
int md=1e9+7;
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int h,w;cin>>h>>w;
for(int i=0;i<=h;i++)dp[i][0]=1;
for(int i=0;i<=w;i++)dp[0][i]=1;
for(int i=1;i<=h;i++){
for(int j=1;j<=w;j++){
dp[i][j]=(dp[i][j]+dp[i-1][j-1]*j*4+dp[i-1][j])%md;
if(j>1)dp[i][j]=(dp[i][j]+dp[i-1][j-2]*(j)*(j-1)/2)%md;
if(i>1)dp[i][j]=(dp[i][j]+(i-1)*j*dp[i-2][j-1])%md;
}
}
cout<<(dp[h][w]-1+md)%md<<"\n";
}
//ill finish later
