#include <iostream>
#include <unordered_map>

using namespace std;

int main() {
    int N;
    cin >> N;

    unordered_map<int, int> freq;
    int a;

    for (int i = 0; i < N; ++i) {
        cin >> a;
        freq[a]++;
    }

    int pairs = 0;
    for (auto &x : freq) {
        pairs += x.second / 2;
    }

    cout << pairs << endl;
    return 0;
}