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.awt.Desktop;




import java.io.BufferedReader;


import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URI;
import java.net.URISyntaxException;
import java.sql.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeSet;
import java.util.Vector;

import org.w3c.dom.Node;





public  class codechef3 {
static class comp implements Comparator<Integer>
{

	
	
	
	@Override
	public int compare(Integer o1, Integer o2) {
		if(Math.abs(o1)>Math.abs(o2))
			return -1;
		else return 1;
	
	}
	
	}
      //=======================================================
	  //sorting Pair
   static class comp1 implements Comparator<Pair<Integer,Integer>>
   {

	@Override
	public int compare(Pair<Integer, Integer> o1, Pair<Integer, Integer> o2) {
		if(o1.k>o2.k)
			return 1;
		else return -1;
	
	}

	
	
	}
        //======================================================= 
	   
   //Creating Pair class  
         //----------------------------------------------------------------------
	    
       static class Pair<Integer,Intetger>
       {
    	   int k=0;
    	   int v=0;
    	   public Pair(int a,int b)
    	   {
    		   k=a;
    		   v=b;
    	   }
    	   public int getKey()
    	   {
    		   return k;
    		   
    	   }
    	   
    	   
       }
    
     //--------------------------------------------------------------------------
	
		 //gcd of two number
		 
		    public static int gcd(int a, int b)
		    {
		      if (b == 0)
		        return a;
		      return gcd(b, a % b); 
		    }
		    
		 //--------------------------------------------------------------------------------------------
		 
		 //lcm of two number
		 static int x;
		    public static int lcm(int a, int b)
		    {
		        return (a / gcd(a, b)) * b;
		    }
		 
		    
		    static class FastReader
		    {BufferedReader br; 
		        StringTokenizer st; 
		 public FastReader() 
		        {  br = new BufferedReader(new
		                     InputStreamReader(System.in)); 
		        } 
		  
		       String next() 
		        { 
		            while (st == null || !st.hasMoreElements()) 
		            { 
		                try
		                { 
		                    st = new StringTokenizer(br.readLine()); 
		                } 
		                catch (IOException  e) 
		                { 
		                    e.printStackTrace(); 
		                } 
		            } 
		            return st.nextToken(); 
		        } 
		  
		        int nextInt() 
		        { 
		            return Integer.parseInt(next()); 
		        } 
		  
		        long nextLong() 
		        { 
		            return Long.parseLong(next()); 
		        } 
		  
		        double nextDouble() 
		        { 
		            return Double.parseDouble(next()); 
		        } 
		  
		        String nextLine() 
		        { 
		            String str = ""; 
		            try
		            { 
		                str = br.readLine(); 
		            } 
		            catch (IOException e) 
		            { 
		                e.printStackTrace(); 
		            } 
		            return str; 
		        } 
		    } 
		  
		    public static boolean isprime(long n)
		    {
		    	for(int i=2;i*i<=n;i++)
		    	{
		    		if(n%i==0)
		    			return false;
		    	}
		    	return true;
		    }
		    
		  //-------------------------------------------------------------------------------------------
		
		    public static void main(String[] args) 
		    {
		    	
		    	
		    	FastReader s=new FastReader();
		        int n=s.nextInt();
		        ArrayList<Integer>[] a=new ArrayList[n];
		        for(int i=0;i<n;i++)
		        	a[i]=new ArrayList<Integer>();
		        for(int i=1;i<n;i++)
		        {
		        	int x=s.nextInt();
		        	a[x-1].add(i);
		        }
		        int flag=0;
		      
		        for(int i=0;i<n;i++)
		        {
		        	if(a[i].size()==0)
		        		continue;
		        	int count=0;
		        	int count1=0;
		        	for(int x:a[i])
		        	{
		        		if(a[x].size()==0)
		        			count++;
		        		if(a[x].size()==0)
		        			count1++;
		        		if(count==3)
		        		{
		        			
		        			break;
		        		}
		        	}
		        	
		        	if(count<3&&count1>0||count<3)
		        	{
		        		flag=1;
		        		break;
		        	}
		        	
		        	
		        }
		        
		        if(flag==0)
		        	System.out.println("YES");
		        else System.out.println("NO");
		        
		   
		    
		    
		    
		    
		        }   	

}