#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000 + 7;
const double esp = 1e-13;
const double pi = 3.141592653589;
long long canhai(long long n) {
  long long fi, la, mid;
  fi = 0;
  la = n + 1;
  while (fi + 1 < la) {
    mid = fi / 2 + la / 2;
    if (fi % 2 && la % 2) mid++;
    if (mid > n / mid)
      la = mid;
    else
      fi = mid;
  }
  return fi;
}
long long power(long long a, long long n, long long m) {
  if (n == 0) return 1;
  long long tmp, c;
  tmp = c = a;
  n--;
  while (n) {
    if (n % 2) tmp = tmp * c % m;
    c = c * c % m;
    n /= 2;
  }
  return tmp;
}
int n, x, f[100 + 10], ans, vt;
int main() {
  cin >> n;
  for (long long i = 1; i <= n; i++) {
    cin >> x;
    f[x]++;
  }
  ans = 0;
  while (true) {
    vt = 0;
    for (long long i = 1; i <= 100; i++)
      if (f[i] >= 2) {
        vt = i;
        break;
      }
    if (!vt) break;
    for (long long i = 1; i <= 100; i++)
      if (i != vt && f[i] >= 2) {
        f[i] -= 2;
        f[vt] -= 2;
        ans++;
        goto loop;
      }
    if (f[vt] >= 4) {
      f[vt] -= 4;
      ans++;
    } else
      break;
  loop:;
  }
  cout << ans;
}
