using System;

public class Program

{

    public static void Main()

    {

        string s1 = "1";

        string s2 = "12";

        string s3 = "123";

        string s4 = "1234";

        string s5 = "12345";

        string s6 = "123456";

        int padBy1 = 6 - s1.Length;

        int padBy2 = 6 - s2.Length;

        int padBy3 = 6 - s3.Length;

        int padBy4 = 6 - s4.Length;

        int padBy5 = 6 - s5.Length;

        int padBy6 = 6 - s6.Length;

        string output1 = new String('0', padBy1) + s1;

        string output2 = new String('0', padBy2) + s2;

        string output3 = new String('0', padBy3) + s3;

        string output4 = new String('0', padBy4) + s4;

        string output5 = new String('0', padBy5) + s5;

        string output6 = new String('0', padBy6) + s6;

        Console.WriteLine(output1);

        Console.WriteLine(output2);

        Console.WriteLine(output3);

        Console.WriteLine(output4);

        Console.WriteLine(output5);

        Console.WriteLine(output6 + "\n");

        Console.WriteLine(String.Format("{0:N6} Doesn't work...\n", s1)); // Doesn't work.

        Console.WriteLine(s1.PadLeft(6, '0'));

        Console.WriteLine(s2.PadLeft(6, '0'));

        Console.WriteLine(s3.PadLeft(6, '0'));

        Console.WriteLine(s4.PadLeft(6, '0'));

        Console.WriteLine(s5.PadLeft(6, '0'));

        Console.WriteLine(s6.PadLeft(6, '0'));

        Console.WriteLine(string.Format("\n{0:000000} Doesn't work...", s1));

    }

}