#include <iostream>
#include <cassert>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;

int main() {
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; ++i) cin >> a[i];
	
	assert(1 <= n && n <= 200000);
	for (int i = 0; i < n; ++i) assert(1 <= a[i] && a[i] <= n);
	
	vector<int> cnt(n);
	for (int i = 0; i < n; ++i) cnt[a[i]] += 1;
	int ans = 0;
	for (int i = 1; i <= n; ++i) ans += cnt[i] / 2;
	cout << ans << endl;
}