int main()
{
	int a[16], i, j, k, count;			//????a???????count????????????
	while(1)
	{
		for ( i = 0; ; i++ )			
		{
			cin>>a[i];					//????
			if ( a[i] == 0 )			//????0?????????
				break;
			if ( a[0] == -1)			
				break;
		}
		if ( a[0] == -1 )				//????????-1???????
			break;
		count = 0;						//?count??0
		for ( k = 0; k < i; k++ )
			for ( j = 0; j < i; j++ )
				if ( ( a[k] == 2 * a[j] ) || ( a[j] == a[k] * 2 ) )
					count++;			//????????????
				cout<<count/2<<endl;	
				}
	return 0;
}
