using System;

using System.Collections.Generic;

public class Program

{

    static List<string> data = new List<string> { "2", "frog", "ball", "20"};

    public static void Main()

    {

    Console.WriteLine("First number: " + data[0]);  

    Console.WriteLine("First Item: " + data[2]);

    data[0] = "100";    

    data.Add("pineapple");

    data.Remove("frog");

    int num1 = int.Parse(data[0]);

    int num2 = int.Parse(data[3]);  

    Console.WriteLine("Sum of first two numbers: " + (num1 + num2));

    }

}