text: #include <bits/stdc++.h>
  
  using namespace std;
  
  vector<string> split_string(string);
  
  // Complete the sockMerchant function below.
  int sockMerchant(int n, vector<int> ar) {
      int max_index = *std::max_element(ar.begin(), ar.end());
      std::vector<int> socks_by_color(max_index+1);
      for (const auto sock : ar) {
          ++socks_by_color[sock];
      }
      int pair_count{0};
      for (const auto socks_count : socks_by_color) {
          pair_count += static_cast<int>(socks_count/2);
      }
      return pair_count;
  }
  
  int main()
  {
      ofstream fout(getenv("OUTPUT_PATH"));
  
      int n;
      cin >> n;
      cin.ignore(numeric_limits<streamsize>::max(), '\n');
  
      string ar_temp_temp;
      getline(cin, ar_temp_temp);
  
      vector<string> ar_temp = split_string(ar_temp_temp);
  
      vector<int> ar(n);
  
      for (int i = 0; i < n; i++) {
          int ar_item = stoi(ar_temp[i]);
  
          ar[i] = ar_item;
      }
  
      int result = sockMerchant(n, ar);
  
      fout << result << "\n";
  
      fout.close();
  
      return 0;
  }
  
  vector<string> split_string(string input_string) {
      string::iterator new_end = unique(input_string.begin(), input_string.end(), [] (const char &x, const char &y) {
          return x == y and x == ' ';
      });
  
      input_string.erase(new_end, input_string.end());
  
      while (input_string[input_string.length() - 1] == ' ') {
          input_string.pop_back();
      }
  
      vector<string> splits;
      char delimiter = ' ';
  
      size_t i = 0;
      size_t pos = input_string.find(delimiter);
  
      while (pos != string::npos) {
          splits.push_back(input_string.substr(i, pos - i));
  
          i = pos + 1;
          pos = input_string.find(delimiter, i);
      }
  
      splits.push_back(input_string.substr(i, min(pos, input_string.length()) - i + 1));
  
      return splits;
  }
  