import java.util.ArrayList;

public class SimpleStack<T> {
    private ArrayList<T> elements;

    public SimpleStack() {
        elements = new ArrayList<>();
    }

    public void push(T elem) {
        elements.add(elem);
    }

    public T pop() {
        return elements.remove(elements.size()-1);
    }

    public int size() {
        return elements.size();
    }
}