#include <bits/stdc++.h>
using namespace std;
const int maxn = 105;
const int MAXN = 30001;
const int logn = 20;
const int inf = (int)1e9;
const int alpha = 26;
const int my_hash = 31;
const long long base = (long long)1e9;
const long long my_mod = 2674894331;
const long long l_inf = (long long)4e18;
const long long mod = (long long)1e9 + 7;
const long long l_mod = (long long)1e18 - 11;
const double fi = (sqrt(5.0) + 1) / 2.0;
const double pi = acos(-1.0);
const double eps = 1e-10;
const double EPS = 0.00005;
int main() {
  ios_base::sync_with_stdio(0);
  srand(time(NULL));
  int n, ans = 0;
  scanf("%d ", &n);
  vector<int> cnt(maxn);
  for (int i = 0; i < n; i++) {
    int len;
    scanf("%d ", &len);
    cnt[len]++;
  }
  for (int i = 0; i < maxn; i++) ans += cnt[i] / 2;
  printf("%d", ans / 2);
}
