import java.util.*;

public class IntStack {

  private Node top;

  private class Node {

    private int data;
    private Node next;

    private Node(int item) {
      data = item;
      next = null;
    }

  }

  public IntStack () {
    top = null;
  }

  public void push(int item) {
    Node n = new Node(item);

    n.next = top;
    top = n;
  }

  public int pop() throws EmptyStackException {
    int v;
 
    if ( top == null )
      throw new EmptyStackException();

    v = top.data;
    top = top.next;

    return v;
  }

  public int peek() throws EmptyStackException {
    if ( top == null )
      throw new EmptyStackException();

    return top.data;
  }

  public void dumpStack() {
    Node p = top;

    while ( p != null ) {
      System.out.println(p.data);
      p = p.next;
    }
  }

  public boolean isEmpty() {
    return top == null;
  }
}