#include <bits/stdc++.h>
using namespace std;
int compare(const void* a, const void* b) { return (*(int*)a - *(int*)b); }
int rez[101];
int main() {
  int n, count = 0;
  int arr[100];
  cin >> n;
  for (int j = 0; j < n; ++j) {
    cin >> arr[j];
    ++rez[arr[j]];
  }
  for (int j = 1; j <= 100; ++j) {
    if (rez[j] > 1 && rez[j] % 2 == 0)
      count += rez[j];
    else if (rez[j] > 1 && rez[j] % 2 != 0)
      count += rez[j] - 1;
  }
  cout << count / 4;
  return 0;
}
