#include<bits/stdc++.h>
using namespace std;
#define int long long
const int MOD = 1e9+7;
int put(int a, int exp)
{
if(exp==0)
return 1;
if(exp%2==0)
return put((a*a)%MOD,exp/2);
else
return (put((a*a)%MOD,exp/2)*a)%MOD;
}
int cm[3005][3005];
int fact[6005];
int comb(int x, int y)
{
return cm[x][y];
}
int place2(int cntl, int m)
{
int aux2 = 1;///aux2 = m * (m-1) * (m-2) * ... * (m-2*cntl+1) / put(2,cntl)
for(int i=0;i<2*cntl;i++)
aux2 = (aux2 * (m-i))%MOD;
aux2 = (aux2 * put(put(2,cntl),MOD-2))%MOD;
return aux2;
}
int calc2(int n, int m)
{
int sum=0;
for(int cntl=0;cntl<=min(n,m/2);cntl++)
{
int aux = (comb(n,cntl) * place2(cntl,m))%MOD;
for(int cntc=0;cntc<=min(m-2*cntl,(n-cntl)/2);cntc++)
{
sum += (aux * ((comb(m-2*cntl,cntc) * place2(cntc,n-cntl))%MOD))%MOD;
sum %= MOD;
}
}
return sum;
}
signed main()
{
fact[0]=1;
for(int i=1;i<=6000;i++)
fact[i]=(fact[i-1]*i)%MOD;
for(int i=0;i<=3000;i++)
{
for(int j=0;j<=i;j++)
{
if(i==j)
cm[i][j]=1;
else if(j==0)
cm[i][j]=1;
else
cm[i][j]=(cm[i-1][j-1]+cm[i-1][j])%MOD;
}
}
int n,m;
cin>>n>>m;
int sum=MOD-1;
for(int cnt1=0;cnt1<=min(n,m);cnt1++)
{
int moduri1 = (((((comb(n,cnt1) * comb(m,cnt1))%MOD)*fact[cnt1])%MOD) * put(4,cnt1))%MOD;///in cate moduri putem pune corturile care sunt singure pe rand si coloana
int moduri2 = calc2(n-cnt1,m-cnt1);
sum += (moduri1 * moduri2)%MOD;
sum %= MOD;
}
cout<<sum;
return 0;
}
/**
*/
