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.*;
import java.lang.*;
import java.io.*;
 
public final class Main
{
    public static void main (String[] args) throws java.lang.Exception {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        ArrayList<Integer>[] adj = new ArrayList[n+1];
        for(int i =1; i<=n ; i++) {
          adj[i]= new ArrayList<>();
        } 
 
        for(int i = 2; i<=n; i++)
           adj[in.nextInt()].add(i);
 
        for(int i =1; i<=n ; i++) {
          int count =0;
          if(adj[i].size()!=0){
            for(int j : adj[i]){
              if(adj[j].size()==0) count++;
            }
            if(count<3){
              System.out.println("No");
              return;
            }
          }
        }
 
        System.out.println("yes");      
 
    }
}