#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
const ll mod=1000000007;
ll n,i,j,k,l,r,x,y,z,w,s,t,two[11000],four[11000],invtwo[11000],fac[11000],invfac[11000],m,dp[3300][3300],b[3300][3300];
ll inv(ll x)
{
ll y=mod-2,s=1;
while(y)
{
if(y&1)
{
s=s*x%mod;
}
x=x*x%mod;
y>>=1;
}
return s;
}
ll C(ll x,ll y)
{
if(x<0)
return 0;
if(y<0||y>x)
return 0;
return fac[x]*invfac[y]%mod*invfac[x-y]%mod;
}
ll g(ll n,ll m)
{
ll i,j,s=0;
if(n<0||m<0)
return 0;
if(n==0||m==0)
return 1;
for(i=0;i<=m&&n-i*2>=0;i++)
{
s=(s+C(m,i)*C(n,2*i)%mod*fac[i*2]%mod*invtwo[i]%mod*dp[n-2*i][m-i]%mod)%mod;
}
return s;
}
ll f(ll n,ll m)
{
ll i,j,s=0;
if(n>m)
swap(n,m);
for(i=0;i<=n;i++)
{
s=(s+C(n,i)*C(m,2*i)%mod*fac[i*2]%mod*invtwo[i]%mod*g(n-i,m-2*i))%mod;
}
return s;
}
int main()
{
for(i=0;i<=3000;i++)
{
dp[i][0]=1;
dp[0][i]=1;
b[0][i]=1;
b[i][0]=i+1;
}
for(i=1;i<=3000;i++)
{
for(j=1;j<=3000;j++)
{
dp[i][j]=1+(b[i-1][j-1])*4%mod*j%mod;
dp[i][j]%=mod;
b[i][j]=(b[i-1][j]+dp[i][j])%mod;
}
}
scanf("%lld %lld",&n,&m);
fac[0]=1;
invfac[0]=1;
for(i=1;i<=10000;i++)
{
fac[i]=fac[i-1]*i%mod;
invfac[i]=inv(fac[i]);
}
two[0]=1;
invtwo[0]=1;
for(i=1;i<=10000;i++)
{
two[i]=two[i-1]*2%mod;
invtwo[i]=inv(two[i]);
}
four[0]=1;
for(i=1;i<=10000;i++)
{
four[i]=four[i-1]*4%mod;
}
s=f(n,m);
s=(s+mod-1)%mod;
printf("%lld",s);
}
