#include <iostream>
#include <algorithm>
using namespace std;

int main(){
   int ans = 0,count,n;
   cin >> n;
   long long a[n];
   for(int i = 0;i < n;i++) cin >> a[i];
   for(int i = 0;i < n;i++){
      count = 0;
      for(int j = 0;j < n;j++) if(a[i] == a[j]) count++;
      if(count == 2) ans++;
   }
   cout << ans << endl;
}