import java.util.*;

public class OurStack2 {

    ArrayList<Character> array;
    int top;

    public OurStack2 ()
    {
	// Can be unlimited in size now.
	array = new ArrayList<Character>();
	top = 0;
    }

    public void push (char ch)
    {
        // INSERT YOUR CODE
    }

    public char pop ()
    {
        // INSERT YOUR CODE
    }


    public boolean isEmpty ()
    {
        // INSERT YOUR CODE
    }

}