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:
/*
 * akshaygupta26
 */
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.Scanner; 
import java.util.Random;
import java.util.Arrays;
import java.util.StringTokenizer; 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Collections;
import java.util.*;
public class B 
{ 
    public static void main(String[] args) 
	{ 
		FastReader sc=new FastReader(); 
		StringBuffer ans=new StringBuffer();
		int test=1;
		while(test-->0)
		{
			int n=sc.nextInt();
			int par[]=new int[n+1];
			int nos[]=new int[n+1];
			for(int i=2;i<=n;i++) {
				int t=sc.nextInt();
				par[i]=t;
				nos[t]++;
			}
			int lc[]=new int[n+1];
			for(int i=1;i<=n;i++) {
				if(nos[i] != 0)continue;
				lc[par[i]]++;
			}
			
			for(int i=1;i<=n;i++) {
				if(nos[i] != 0) {
					if(lc[i]<3) {
						System.out.println("No\n");
						System.exit(0);
					}
				}
			}
			
			
			ans.append("Yes\n");
			
			
		
		}
		
	    System.out.print(ans);
	} 
    
    static String convertString(ArrayList<Integer> li) {
    	StringBuffer s1=new StringBuffer();
    	for(int x:li) s1.append(x+" ");
    	return s1.toString().trim();
    }
    
    static String getRes(String key,int n) {
    	String res="";
    	String keys[]=key.split(" ");
    	int i=1;
    	for(String value:keys) {
    		int val =Integer.parseInt(value);
    		while(i<val) {
    			res+="1";
    			++i;
    		}
    		++i;
    		res+="0";
    	}
    	while(i<=n) {
    		res+="1";
    		++i;
    	}
    	return res;
    }
    
    static final Random random=new Random();
    
	static void ruffleSort(int[] a) {
		int n=a.length;//shuffle, then sort 
		for (int i=0; i<n; i++) {
			int oi=random.nextInt(n), temp=a[oi];
			a[oi]=a[i]; a[i]=temp;
		}
		Arrays.sort(a);
	}
	
	static void ruffleSort(long[] a) {
		int n=a.length;//shuffle, then sort 
		for (int i=0; i<n; i++) {
			int oi=random.nextInt(n);
			long temp=a[oi];
			a[oi]=a[i]; a[i]=temp;
		}
		Arrays.sort(a);
	}
	
	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; 
		} 
	} 


}