import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Student implements Comparable<Student>{
    private int id;
    private String name;
    Student(int id,String name){
        this.id=id;
        this.name=name;
    }
    public int compareTo(Student s){
        return this.id-s.id;
    }
    public String toString(){
        return id+" "+name;
    }
}
class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
        List<Student> list=new ArrayList<>();
        list.add(new Student(1,"kusuma"));
        list.add(new Student(3,"eishwa"));
        list.add(new Student(2,"bhaskari"));
        Collections.sort(list);
        System.out.println(list);
    }
}