import java.util.*;

public class Test{
	static int sumNodes(Tree t){
		Enumeration e=t.nodes();
		int sum=0;

		while(e.hasMoreElements())
			sum+=((Leaf)e.nextElement()).value;
		return sum;
		}

	public static void main(String args[]){
		Tree t=new Node(new Leaf(3), new Leaf(4));
		System.out.println("Sum of leaves="+sumNodes(t));
		}
	}