#include <bits/stdc++.h>
using namespace std;
void housekeeping() { ios_base::sync_with_stdio(false); }
int a[123];
int hs[123];
int main() {
  housekeeping();
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    hs[a[i]]++;
  }
  int f = 0, h = 0;
  for (int i = 1; i <= 100; i++) {
    if (hs[i] >= 2 && hs[i] < 4)
      h++;
    else if (hs[i] >= 4) {
      f += hs[i] / 4;
      hs[i] %= 4;
      if (hs[i] >= 2) h++;
    }
  }
  cout << f + h / 2 << endl;
}
