#include <bits/stdc++.h>
#pragma comment(linker, "/stack:67108864")
using namespace std;
template <class T>
T abs(T a) {
  return (a) > 0 ? (a) : -(a);
}
template <class T>
T sqr(T a) {
  return (a) * (a);
}
const long double PI = 3.1415926535897932, EPS = 1E-9;
const int INF = 1000 * 1000 * 1000, NMAX = 111;
long double dist(pair<long double, long double> a,
                 pair<long double, long double> b) {
  return sqrtl(sqr(a.first - b.first) + sqr(a.second - b.second));
}
int main() {
  int n;
  cin >> n;
  int a[NMAX];
  for (int i = 0; i < int(NMAX); ++i) a[i] = 0;
  for (int i = 0; i < int(n); ++i) {
    int t;
    cin >> t;
    a[t]++;
  }
  int cnt = 0;
  for (int i = 0; i < int(NMAX); ++i)
    for (int j = 0; j < int(NMAX); ++j)
      if (i != j) {
        if ((a[i] / 2) != 0 && (a[j] / 2) != 0) {
          int c = min(a[i] / 2, a[j] / 2);
          cnt += c;
          a[i] -= c * 2;
          a[j] -= c * 2;
        }
      }
  for (int i = 0; i < int(NMAX); ++i) {
    cnt += (a[i] / 4);
  }
  cout << cnt;
  return 0;
}
