#include <bits/stdc++.h>
using namespace std;
int i, n, q, ans, j;
int a[201010];
int main() {
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> q;
    a[q]++;
  }
  for (i = 1; i <= 100; i++) {
    for (j = i + 1; j <= 100; j++) {
      q = min(a[i], a[j]);
      q /= 2;
      ans += q;
      a[i] -= q * 2;
      a[j] -= q * 2;
    }
  }
  for (i = 1; i <= 100; i++) ans += a[i] / 4;
  cout << ans;
  return 0;
}
