int main()
{
	int n=0,m[20],i=0,j=0,t=0;//n is the num of int
	char c;
	scanf("%d%c",&m[0],&c);
	while(m[0]>0)
	{
		n=1;
		t=0;
		while(c!='\n')
			scanf("%d%c",&m[n++],&c);
		n--;
		for(i=0;i<n;i++){
			for(j=n;j>i;j--)
				if((m[j]==2*m[i])||(m[i]==2*m[j]))	t++;
		}
		printf("%d\n",t);
		scanf("%d%c",&m[0],&c);
	}
	return 0;
}