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

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");

        int ii = 1;
        int jj = 2;
        double kk = 2.13;
        double ll = 2.1300;
        String ss = "";
        double iid = (double)ii;
        System.out.println(ii+"_"+jj+"_"+kk+"_"+ll+"_");
    
    }
}