#include <bits/stdc++.h>
using namespace std;
template <class T>
T gcd(T a, T b) {
  return b <= 0 ? a : gcd(b, a % b);
}
template <class T>
T lcm(T a, T b) {
  return (a * b) / gcd(a, b);
}
template <class T>
T large(T a, T b) {
  return a > b ? a : b;
}
template <class T>
T small(T a, T b) {
  return a < b ? a : b;
}
template <class T>
T dif(T a, T b) {
  return a - b < 0 ? b - a : a - b;
}
template <class T>
string toStr(const T &x) {
  stringstream s;
  s << x;
  return s.str();
}
template <class T>
int toInt(const T &x) {
  stringstream s;
  s << x;
  int r;
  s >> r;
  return r;
}
void in() {}
long long int fib(long long int x) {
  if (x == 1 || x == 0)
    return x;
  else
    return fib(x - 1) + fib(x - 2);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  vector<int> v;
  map<int, int> m1;
  int n, i, a;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a;
    m1[a]++;
  }
  for (auto it : m1) {
    if (it.second & 1 && it.second != 1)
      v.push_back(it.second - 1);
    else if (it.second != 1)
      v.push_back(it.second);
  }
  sort(v.begin(), v.end(), greater<int>());
  int sum = 0;
  for (i = 0; i < ((int)(v).size()); i++) {
    sum += v[i];
  }
  sum /= 4;
  cout << sum << endl;
  return 0;
}
