using System;

public class Program

{

    public static void Main()

    {

        //Challenge 1

        int a = 1;

        for(int n=1; n != 20; a = n + a)

        {

            Console.WriteLine(a);

            n = n + 1;

        }

        Console.WriteLine("");

        //Challenge 2

        Console.WriteLine("What number would you like to end on? ");

        int n2 = 0; 

        int c = 0;

        int.TryParse(Console.ReadLine(), out c);

        for(int b=1; n2 != c; b = n2 + b)

        {

            Console.WriteLine(b);

            n2 = n2 + 1;

        }

    }

}