// Project: Loops
// Module: hailstone
// Source code file: Main.java
// Given the start value, generate the Hailstone sequence:
// If n is even n = n / 2, otherwise n = 3 * n + 1.
// The sequence is called a Hailstone sequence because its
// values move up and down in an unpredictable manner, similar
// to hailstones in a thunderstorm cloud.
// Mathematicians believe that all Hailstone sequences terminate
// with one, even though they have not been able to formally prove this
// for all starting values.

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {

        // Create Scanner object.
        Scanner input = new Scanner(System.in);

        // Display input prompt.
        System.err.print("Enter start value for Hailstone sequence: ");

        // Get start value.
        int startValue = input.nextInt( );
        int counter = 1;
        for(int n = startValue; n > 1; ) {
            if (n % 2 == 0) {
                n /= 2;
            }
            else {
                n = 3 * n + 1;
            }
            counter++;
            System.out.print(n + " ");
            if (counter % 20 == 0) {
                System.out.println( );
            }
        }

        // Close Scanner object.
        input.close( );
    }
}