#include <bits/stdc++.h>
using namespace std;
const int OO = (int)1e8;
const double EPS = 1e-11;
int diri[] = {0, 1, -1, 0};
int dirj[] = {1, 0, 0, -1};
int arr[101];
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; ++i) cin >> v[i];
  for (int i = 1; i < 101; ++i)
    for (int j = 0; j < n; ++j) arr[i] += (v[j] == i);
  int ret = 0;
  for (int i = 1; i < 101; ++i) {
    if (arr[i] < 2) continue;
    for (int j = 1; j < 101; ++j) {
      if (arr[j] < 2) continue;
      int a = arr[j] / 2, b = arr[i] / 2;
      arr[i] -= min(a, b) * 2;
      arr[j] -= min(a, b) * 2;
      ret += min(a, b);
    }
  }
  cout << ret / 2;
  return 0;
}
