#include <bits/stdc++.h>
int fre[101];
using namespace std;
int main() {
  int n, x, sum = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x;
    fre[x]++;
  }
  for (int i = 1; i <= 100; i++) {
    sum += fre[i] / 2;
  }
  cout << sum / 2;
}
