#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(101, 0);
  for (typeof(0) i(0); i != (n); ++i) {
    int x;
    cin >> x;
    v[x]++;
  }
  for (typeof(1) i(1); i != (101); ++i) v[i] /= 2;
  int count = 0, flag = 0;
  for (typeof(1) i(1); i != (101); ++i) {
    if (v[i]) {
      if (v[i] % 2 == 0)
        count += v[i] / 2;
      else {
        count += v[i] / 2;
        if (flag) {
          count++;
          flag = 0;
        } else
          flag = 1;
      }
    }
  }
  cout << count;
  return 0;
}
