#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t;
  int numeros[100] = {0};
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> t;
    numeros[t - 1] += 1;
  }
  t = 0;
  for (int i = 0; i < 100; i++) {
    t += numeros[i] / 2;
  }
  cout << t / 2;
}
