#include <bits/stdc++.h>
using namespace std;
const long long mod=1e9+7;
long long n,m;
long long dp[3001][3001];
void solve()
{
cin>>n>>m;
dp[0][0]=1;
for(long long i=1;i<=n;i++)
dp[i][0]=1;
for(long long i=1;i<=m;i++)
dp[0][i]=1;
for(long long i=1;i<=n;i++)
{
for(long long j=1;j<=m;j++)
{
dp[i][j]=dp[i-1][j];
dp[i][j]%=mod;
if(i>=2)dp[i][j]+=dp[i-2][j-1]*j*(i-1);
dp[i][j]%=mod;
if(j>=2)dp[i][j]+=dp[i-1][j-2]*(j-1)*j/2;
dp[i][j]%=mod;
dp[i][j]+=dp[i-1][j-1]*j*4;
dp[i][j]%=mod;
//cout<<i<<" "<<j<<" "<<dp[i][j]<<endl;
}
}
cout<<dp[n][m]-1<<endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
solve();
return 0;
}
