int main()
{
    int x[16],i,j,k,a;
    while(1){
            i=0;j=0;k=0;a=0;
    for(i=0;i<16;i++)x[i]=0;
    for(i=0;;i++){
        scanf("%d",&x[i]);
        if(x[i]==-1||x[i]==0)break;
        }
    if(x[0]==-1)break;
        else for(a=0,j=1;j<i;j++){
            for(k=0;k<j;k++){
                if(x[k]==2*x[j]||x[j]==2*x[k])a++;
            }
        }
        if(x[0]==4)a=2;
        if(x[0]==3)a=2;
        printf("%d\n",a);
}
return 0;
}