using System;

using System.Text;  

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        //var f=new HashSet<string>(Array.Empty<string>());

        var gf=new HashSet<string>(new IEQCompare()){"KISHOR","KIshor"};

        var g1=new HashSet<string>(new IEQCompare()){"kishor"};

        var fg =gf.Union(g1,new IEQCompare());

        fg.Dump();

    }

        public class IEQCompare:IEqualityComparer<string>{

            public bool Equals(string x, string y) {  

                return x.Equals(y,StringComparison.InvariantCultureIgnoreCase);

            }  

            public int GetHashCode(string obj) {  

                return obj.GetHashCode();  

            }  

        }

}