1 #include<cstdio>  
 2 #include<cstdlib>  
 3 #include<cmath>  
 4 #include<iostream>
 5 #include<algorithm>
 6 int set[200], n[100];
 7 using namespace std;
 8 int main()
 9 {
10     int i = 0,ans=0;
11     while (cin >> n[++i])
12     {
13         if (n[i] == 0) break;
14         set[2 * n[i]] = 1;
15     }
16     i--;
17     for (int j = 1; j <= i; j++)
18     {
19         if (set[n[j]]) ans++;
20     }
21     cout << ans;
22     return 0;
23 }