#include <bits/stdc++.h>
using namespace std;
int a[110], b[110], n, i, j, k, m;
int main() {
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> m;
    for (k = 0; k < j; k++)
      if (a[k] == m) {
        b[k]++;
        break;
      }
    if (k == j) a[j] = m, b[j] = 1, j++;
  }
  m = 0;
  for (i = 0; i < j; i++) {
    while (i < j && b[i] >= 2) {
      b[i] -= 2;
      k = i;
      while (k < j && b[k] < 2) k++;
      if (k < j)
        m++, b[k] -= 2;
      else
        i = k;
    }
  }
  cout << m;
  return 0;
}
