#include <bits/stdc++.h>
using namespace std;
int cnt[101];
int main() {
  int n, k;
  while (cin >> n) {
    memset(cnt, 0, sizeof(cnt));
    while (n--) {
      cin >> k;
      cnt[k]++;
    }
    for (int i = 0; i <= 100; i++) cnt[i] /= 2;
    int ans = 0;
    for (int i = 0; i <= 100; i++) ans += cnt[i];
    if (ans & 1) ans--;
    cout << ans / 2 << endl;
  }
  return 0;
}
