#include<bits/stdc++.h>
#define reg register
// #define int long long
inline int read(){
    reg int x=0,k=1; reg char ch=getchar();
    while (ch<'0'||ch>'9') (ch=='-')&&(k=-1),ch=getchar();
    while (ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
    return x*k;
}
const int N=3010,mod=1e9+7;
int n,m,C[N][N],ipw[N*2],fac[N*3];
signed main(){
    n=read(),m=read();
    ipw[0]=1; for (reg int i=1;i<=n+m;i++) ipw[i]=ipw[i-1]*(mod+1ll>>1)%mod;
    fac[0]=1; for (reg int i=1;i<=n*3;i++) fac[i]=1ll*fac[i-1]*i%mod;
    for (reg int i=0;i<=n||i<=m;i++) C[i][0]=1;
    for (reg int i=1;i<=n||i<=m;i++) for (reg int j=1;j<=i;j++) C[i][j]=(C[i-1][j]+C[i-1][j-1])%mod;
    reg int res=0;
    for (reg int a=0,b;b=n-a,a<=n;a++) for (reg int c=0,d;d=m-c,c<=m;c++) if (a+a+b==c+c+d){
        reg int ans=0;
        for (reg int i=0;i<=a&&i<=c;i++){
            reg int p=1ll*C[n][a]*C[m][c]%mod*C[a][i]%mod*C[c][i]%mod*fac[2*(a-i)+b]%mod*ipw[c-i]%mod*fac[i]%mod;
            if (i&1) ans=(ans+mod-p)%mod; else ans=(ans+p)%mod;
        }
        res=(res+1ll*ans*ipw[a])%mod;
    }
    printf("%d\n",res);
    return 0;
}