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()));
}
}
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