#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, input, i = 0;
  int flag = 0;
  vector<int> v;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> input;
    v.push_back(input);
  }
  sort(v.begin(), v.end());
  while (i < n) {
    if (count(v.begin(), v.end(), v[i]) >= 2) {
      a = v[i];
      v.erase(v.begin() + i);
      v.erase(remove(v.begin(), v.begin() + i, a));
      flag++;
    } else
      i++;
  }
  cout << flag / 2 << endl;
}
