//*********************************
//* ?????? **
//* ???1.cpp **
//* ????????? **
//* ???2012.10.31 **
//*********************************
int main()
{
	int i = 0, j, k, n, t = 0;                            
	int a[16];                                     //??????
	   while (cin >> n)                            //???n?????????
	   {
		 if (n != 0)                                 //???????0?????????????
		 {
		   a[i] = n;
	   	   i++;
		 }
		 else                                        //??????0????????
		 {
		   for (j = 0; j < i - 1; j++)                 //??????????????????
		   {
		      for (k = j + 1; k <= i - 1; k++)          //??????????????????
			  {
		         if (a[k] == 2 * a[j] || a[j] == 2 * a[k]) //????2?????t?1
			      t ++;                               
			  }
		   }
		   cout << t << endl;                          //??t???
		   t = 0;                                     //???????????t???0
		   i = 0;                                        //i???0
		 }	 
	   }
	return 0;
}


