using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var currencies = new List<string>() { "NAD", "ZAR", "BWP", "USD" };

        Console.WriteLine(string.Join(", ", currencies));

        var currency = currencies.FirstOrDefault(c => c == "USD");

        Console.WriteLine(currency);

    }

}