#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<int> ap(N);
    while(N--){
        int a; cin >> a; a--;
        ap.at(a)++;
    }
    int answer = 0;
    for(auto &a : ap) answer += a/2;
    cout << answer << endl;
}