//Letters.java

import java.util.LinkedList;

public class Letters
{
    public static void main(String[] args)
    {
        LinkedList<Character> letters = new LinkedList<Character>();
        Character letter;
        int i;

        letters.add('a');
        letters.add('b');
        letters.add('c');
        letters.add('d');

        letters.add(1, 'e');
        letters.set(2, 'f');
        letters.remove(3);

        for (i = 0; i < letters.size(); ++i)
        {
            letter = letters.get(i);
            System.out.print(letter);
        }
        System.out.println();
    }
}