using System;

using System.Collections.Generic;

using System.Collections;

public class Program

{

    public static void Main()

    {

        string str = "google";

        string output = "";

        List<char> duplicates = new List<char>();

        foreach (char c in str)

        {

            if(duplicates.Contains(c))

                continue;

            else

            {

                output += c.ToString();

                duplicates.Add(c);

            }

        }

        Console.WriteLine("remove duplicates- " + output);

    }

}