#include <bits/stdc++.h>
using namespace std;
int n, a, d[105], ans, i;
int main() {
  while (cin >> n) {
    for (i = 0; i <= n; ++i) d[i] = 0;
    for (ans = 0, i = 0; i < n; ++i) {
      cin >> a;
      d[a]++;
      if (d[a] == 2) {
        ans++;
        d[a] = 0;
      }
    }
    cout << ans / 2 << endl;
  }
}
