#include <bits/stdc++.h>
using namespace std;
int main() {
  long v, i, j, k, l = 0, m, n, p, r, a[500000] = {0}, t1, t2 = 0, te1, te2,
                   c = 0;
  string aa;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> v;
    a[v]++;
  }
  for (i = 0; i < 101; i++) {
    c = c + a[i] / 2;
  }
  cout << c / 2;
  return 0;
}
