import java.util.ArrayList;
import java.util.List;

public class MyStack {
	private List<String> l;
	private int size;
	public String top;

	public MyStack() {
		l = new ArrayList<String>();
		size = 0;
		top = null;
	}

	public int size() {
		return size;
	}

	public void push(String s) {
		l.add(s);
		top = s;
		size++;
	}

	public String pop() {
		String s = l.get(size - 1);
		l.remove(size - 1);
		size--;
		top = size == 0 ? null : l.get(size - 1);
		return s;
	}
}



//java/7795