Merkkijono

import java.util.*;
public class Main {
    public static String line;
    public static char[] lineArray;

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);

        line = s.nextLine();
        lineArray = line.toCharArray();

        CheckChars();
        System.out.println(line);

    }

    public static void CheckChars(){
        for (int i = 0; i < line.length(); i++)
        {
            try
            {
                if (lineArray[i] == lineArray[i + 1])   //There are 2 or more letters next to eachother
                {
                    int x = 0;
                    for (int o = i; o < line.length(); o++)  //Delete as many letters as there are next to eachother
                    {
                        if (lineArray[o] != lineArray[i])
                        {
                            break;
                        }
                        x += 1;
                    }
                    //Console.WriteLine(x);
                    line = line.replace(line.substring(i,x), "");
                    break;
                }
            }
            catch (IndexOutOfBoundsException out)
            {
                break;
            }
        }
        CheckLine();
    }


    public static void CheckLine()  //Check if there are any chars left to remove
    {
        lineArray = line.toCharArray();
        for(int i = 0; i < lineArray.length; i++)
        {
            try
            {
                if (lineArray[i] == lineArray[i + 1])
                {
                    CheckChars();
                }
            } catch(IndexOutOfBoundsException out)
            {
                break;
            }
        }
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: TIME LIMIT EXCEEDED

Test 4

Verdict: TIME LIMIT EXCEEDED

Test 5

Verdict: TIME LIMIT EXCEEDED

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: TIME LIMIT EXCEEDED

Test 10

Verdict: TIME LIMIT EXCEEDED