#include <bits/stdc++.h>
using namespace std;
const int N = 111111;
const int INF = int(1e9), mod = (int)1e9 + 7;
int n, f[111];
int main() {
  cin >> n;
  while (n--) {
    int x;
    cin >> x;
    f[x]++;
  }
  int cnt = 0;
  for (int(i) = (0); (i) < (111); ++(i)) {
    cnt += f[i] >> 1;
  }
  cout << (cnt >> 1);
  return 0;
}
