import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
    static ArrayList<Integer> removeDup(ArrayList<Integer> a) {
		Collections.sort(a);	
		
		int uniqueCnt = 0; 
		for (int i = 0; i < a.size(); ++i) {
			if ((i == 0 || a.get(i) != a.get(i-1)) && (i+1 == a.size() || a.get(i) != a.get(i+1))) {
				a.set(uniqueCnt++, a.get(i));
			}
		} 
		a.subList(uniqueCnt, a.size()).clear();
		return a;
    }
    
    public static void main (String[] args) throws java.lang.Exception
    {
        ArrayList<Integer> values = new ArrayList<>(Arrays.asList(1,2,3,4,4,5,6,7,7,8,9,10,11,11,11,11,11,12,12,13,13,13,13));
        System.out.println(removeDup(values));
        ArrayList<Integer> values2 = new ArrayList<>(Arrays.asList(1,1,2,2,3,3));
        System.out.println(removeDup(values2));
        ArrayList<Integer> values3 = new ArrayList<>(Arrays.asList(1));
        System.out.println(removeDup(values3));
    }
}