// http://www.cs.nyu.edu/courses/summer07/G22.2110-001/hw07-java-intstack.txt
public class IntStack extends IntVector {
  private int top;

  public IntStack() {
    super(5);
    top = 0;
  }

  public void push(int x) {
    if (super.size() <= top)
      resize(2 * super.size());
    set(top, x);
    top++;
  }

  public int pop() {
    top--;
    return get(top);
  }

  public int size() {
    return top;
  }    
}