#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(void) {
    int n;
    cin >> n;

    vector<int> cnt(n+1);
    for (int i = 0; i < n; i++) {
        int a; cin >> a;
        cnt[a]++;
    }

    int ans = 0;
    for (int i = 0; i <= n; i++) {
        ans += cnt[i]/2;
    }

    cout << ans << endl;
    
    return 0;
}