#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a;
  int arr[105];
  memset(arr, 0, sizeof arr);
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a;
    ++arr[a];
  }
  int acum = 0;
  for (int i = 0; i <= 100; ++i) {
    acum += arr[i] / 2;
  }
  cout << acum / 2;
}
