//**************************
//*?????              *
//*?????? 1200012775 *
//*???2012/10/29        *
//**************************
int main()
{
	int a[15], t, i, j, k, m, n;	//????????
	for (i = 1; ; i++)	//????
	{
		for(j = 0; j <= 14; j++)	//??????????0
			a[j] = 0;
		for (j = 0; ; j++)
		{
			cin >> t;	//??
			if (t == 0)	//??????0
				break;	//????
			else	//??
			{
				a[j] = t;	//?????
			}
		}
		m = 1;	//??????
		if (a[0] != -1)	//???????0
			m = 0;	//?????
		for (j = 1; j < 15; j++)
		{
			if (a[j] != 0)	//???????????
				m = 0;	//?????
		}
		if (m == 1)	//?????
		{
			cout << "0" << endl;	//??0
			break;	//??
		}
		n = 0;	//??????0?
		for (j = 0; j <= 14; j++)	//???????
			for (k = j + 1; k <= 14; k++)	//????????
			{
				if(a[j] != 0 && a[k] != 0 && (a[j] == 2 * a[k] || a[k] == 2 * a[j]))	//???????0?????????2?
					n = n + 1;	//???1
			}
		cout << n << endl;	//????
	}
	return 0;
}