using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Input sentence: ");

        string kata = Console.ReadLine().Replace(" ","");

        if(kata == ""){

            Console.WriteLine("Please input sentence!");

        }else{

            string buffer = "";

            char[] huruf = kata.ToCharArray();

            int L = kata.Length;

            int index = 0;

            for(int a=0; a<L; a++){

                buffer += huruf[a];

                for(int b=a+1; b<L; b++){

                    if(huruf[a]==huruf[b]){

                        buffer += huruf[b]; 

                        index = b;

                    }else{

                        buffer += "";

                    }

                }

                huruf[index] = '\0';

            }

            Console.WriteLine(buffer);

        }

    }

}