content: package bell;
  
  import java.io.FileReader;
  import java.io.FileWriter;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Scanner;
  
  public class Bell {
      public static void main(String[] args) throws IOException {
          StringBuilder result = new StringBuilder();
          ArrayList<Integer> data = new ArrayList<>();
  
          Scanner sc = new Scanner(new FileReader("input.txt"));
          while (sc.hasNextLine()){
              String[] symbols = sc.nextLine().split(" ");
              for(String i : symbols){
                  data.add(Integer.valueOf(i));
              }
          }
          data.remove(0);
          Collections.sort(data);
  
          for(int i = 0; i < data.size(); i++){
              if(i % 2 == 0){
                  result.append(data.get(i)).append(" ");
              }
          }
  
          for(int i = data.size()-1; i > 0; i--){
              if(i % 2 == 1){
                  result.append(data.get(i)).append(" ");
              }
          }
  
          FileWriter out = new FileWriter("output.txt");
          out.write(String.valueOf(result).trim());
          out.close();
      }
  }
  