Problem: Consider a rooted tree. A rooted tree has one special vertex called the root. All edges are directed from the root. Vertex u is called a child of vertex v and vertex v is called a parent of vertex u if there exists a directed edge from v to u. A vertex is called a leaf if it doesn't have children and has a parent.

Let's call a rooted tree a spruce if its every non-leaf vertex has at least 3 leaf children. You are given a rooted tree, check whether it's a spruce.

The definition of a rooted tree can be found [here](https://goo.gl/1dqvzz).

Input

The first line contains one integer n — the number of vertices in the tree (3 ≤ n ≤ 1 000). Each of the next n - 1 lines contains one integer pi (1 ≤ i ≤ n - 1) — the index of the parent of the i + 1-th vertex (1 ≤ pi ≤ i).

Vertex 1 is the root. It's guaranteed that the root has at least 2 children.

Output

Print "Yes" if the tree is a spruce and "No" otherwise.

Examples

Input

4
1
1
1


Output

Yes


Input

7
1
1
1
2
2
2


Output

No


Input

8
1
1
1
1
3
3
3


Output

Yes

Note

The first example:

<image>

The second example:

<image>

It is not a spruce, because the non-leaf vertex 1 has only 2 leaf children.

The third example:

<image>

Solution (in JAVA):

Solution:



import java.util.Scanner;
import java.util.Vector;

public class Main{
	
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		int n=Integer.parseInt(scanner.nextLine());
		Vector<Integer> root=new Vector<>();
		Vector<Vector<Integer>> v=new Vector<Vector<Integer>>();
		for(int i=0;i<n-1;i++) {
			int gen=Integer.parseInt(scanner.nextLine());
			if(root.contains(gen)) {
				v.get(root.indexOf(gen)).add(i+2);
			}else {
				root.add(gen);
				Vector<Integer> temp=new Vector<>();
				temp.add(i+2);
				v.add(temp);
			}
		}
		//print
		/*for(int i=0;i<root.size();i++)
			System.out.print(root.get(i)+" ");
		System.out.println("------");
		for(int i=0;i<v.size();i++) {
			for(int j=0;j<v.get(i).size();j++) {
				System.out.print(v.get(i).get(j)+" ");
			}
			System.out.println();
		}*/
		boolean res=true;
		for(int i=0;i<v.size();i++) {
			int child=0;
			for(int j=0;j<v.get(i).size();j++) {
				if(!root.contains(v.get(i).get(j))) {
					child++;
				}
			}
			if(child<3) {
				res=false;
				break;
			}
		}
		String resp=res?"Yes":"No";
		System.out.println(resp);

	}

}