#include <bits/stdc++.h>
using namespace std;
int main() {
  int n = 0, temp = 0, cont = 0, frames = 0;
  int sticks[105];
  int auxiliar[105];
  for (int i = 0; i < 105; ++i) {
    sticks[i] = 0;
    auxiliar[i] = 0;
  }
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> temp;
    sticks[temp]++;
    auxiliar[i] = temp;
  }
  for (int i = 0; i < n; i++) {
    while (sticks[auxiliar[i]] >= 2) {
      sticks[auxiliar[i]] -= 2;
      cont++;
      if (cont % 2 == 0) frames++;
    }
  }
  cout << frames;
  return 0;
}
