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

#define rep(i, n) for( ll i = 0; i < n; i++ )
using ll = long long;

int main() {
	int N;
	cin >> N;
	map<int, int> mp;
	rep(i, N) {
		int a;
		cin >> a;
		mp[a]++;
	}
	int ans = 0;
	for(auto p : mp) {
		ans += p.second / 2;
	}
	cout << ans << endl;
}