import java.util.*;


public class Main{
  
  public static void main(String[] args){
    ArrayList<String> array = new ArrayList<String>();
      
    Scanner scan = new Scanner(System.in);
    //int val = scan.nextInt();
    //System.out.print(val);
    //int val2 = scan.nextInt();
    //System.out.print(val2);
    while(scan.hasNext()){
      array.add(scan.next());
    }
    
    Collections.sort(array);
    
    String val=""; 
    for(int i=2; i<array.size(); i++){
      val = val + array.get(i);
    }
    
    System.out.print(val);
  }
   
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz