#include <bits/stdc++.h>
using namespace std;
int A[101];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    int m;
    cin >> m;
    A[m]++;
  }
  for (int i = 1; i <= 100; i++) {
    A[i] /= 2;
  }
  int k = 0;
  for (int i = 1; i <= 100; i++) {
    for (int j = i; j <= 100; j++) {
      if (A[i] >= 1 && A[j] >= 1) {
        if (i == j && A[i] >= 2) {
          k += A[i] / 2;
          A[i] = A[i] % 2;
        } else if (i != j) {
          int t = min(A[i], A[j]);
          A[i] -= t;
          A[j] -= t;
          k += t;
        }
      }
    }
  }
  cout << k;
  return 0;
}
