using System.IO;
using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void Main()
{
List<string> list1 = new List<string> { "A", "C", "F", "H", "I" };
List<string> list2 = new List<string> { "B", "D", "F", "G", "L" };
String sel = list1.Intersect(list2).FirstOrDefault()??"";
Console.WriteLine(sel);
}
}
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