#include <bits/stdc++.h>
using namespace std;
long long GCD(long long a, long long b) {
  if (b == 0) return a;
  return GCD(b, a % b);
}
long long LCM(long long a, long long b) {
  long long gcd = GCD(a, b);
  return (a * b) / gcd;
}
int main() {
  long long i, j, k, n, m, t, x, y, s = 1, c = 0, l;
  cin >> n;
  int a[n];
  for (i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (i = 0; i < n - 1;) {
    if (a[i] == a[i + 1]) {
      c++;
      i += 2;
    } else {
      i++;
    }
  }
  cout << c / 2 << endl;
}
