using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

//using Useful.String.Extensions;

public class Program

{

    public static void Main()

    {

        string str1 = "abcde";

        string str2 = "abc";

        HashSet<char> a = new HashSet<char>();

        HashSet<char> b = new HashSet<char>();

        //string s1=Console.ReadLine();

        //string s2= Console.ReadLine();

        foreach (char i in str1)

        {

            a.Add(i);

        }

​

        foreach (char j in str2)

        {

            b.Add(j);

        }

​

        a.ExceptWith(b);

        DisplaySet(a);

    }

​

    public static void DisplaySet(HashSet<char> set)

    {

        Console.Write("{");

        foreach (char i in set)

        {

            Console.Write(" {0}", i);

        }

​

        Console.WriteLine(" }");

    }

}