using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

​

        Dictionary<int, string> test = new Dictionary<int, string>();

        test.Add(20, "abc");

        test.Add(18, "cde");

        test.Add(21, "tes");

        string val = string.Join(",", test.Keys);

        Console.WriteLine(val);

        int iVal;

        Console.WriteLine(int.TryParse("", out iVal));

        Console.WriteLine(iVal);

        List<int> test1 = new List<int>();

        test1.Add(20);

        test1.Add(18);

        test1.Add(21);

        string val1 = string.Join(",", test1);

        Console.WriteLine(val1);

    }

}