#include <iostream>
#include <map>
using namespace std;
int main() {
    int n;
    cin >> n;
    map <int, int> m; int d, ans = 0;
    for (int i = 0; i < n; i++) {
        cin >> d;
        auto f = m.find(d);
        if ( f == m.end())
            m.insert(make_pair(d, 1));
        else {
            f->second++;
            if (f->second % 4 == 0)
                ans++;
        }
    }
    cout << ans;
}


Edited by author 30.01.2019 03:14