//???????????????????
//?????11.3
//????wayne
int main()
{
	int n,a[16],i,t,m,j,k,sum;
	while (cin>>t)                  
	{
		if (t!=-1)                  //??????????
		{
			a[1]=t;
			i=1;
			while (cin>>m)
			{
				if (m!=0)          //????????????
				{ 
					i=i+1;
					a[i]=m;        //??????????????????
				}
                else break;       //???????
			}
			sum=0;
			for (j=1;j<=i;j++)
                 for (k=1;k<=i;k++)
				 {
					 if (a[k]==2*a[j]||a[k]==0.5*a[j])  //??????????????
						 sum=sum+1;             //???????1
				 } 
		   cout<<sum/2<<endl;                   //??????????????2
		}
		else {cout<<endl;break;}                //?-1??????
	}
	return 0;
}