using System;
using System.Text;
using System.Linq;
using System.Collections.Generic;
        
public class Program
{
 
public static void Main(string[] args)
{
            List<string> a = new List<string>(){"A","B","C","D"};
            if(a.Count > 1)
                a.RemoveAt(a.Count-2);

            Console.Write(string.Join(",", a.ToArray()));
    }
}