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.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.InputMismatchException;

public class B913{

	void solve()
	{
		int n = ni();
		ArrayList<Integer>[] list = new ArrayList[n+1];
		for(int i=1;i<=n;i++)
			list[i] = new ArrayList<>();
		boolean[] p = new boolean[n+1];
		for(int i=2;i<=n;i++)
		{
			int k = ni();
			p[k] = true;
			list[k].add(i);
		}
//		db(list);
		for(int i=1;i<=n;i++)
			if(p[i])
			{
				int cn = 0;
				for(int x : list[i])
					if(!p[x])
						cn++;
				if(cn < 3)
				{
					out.println("No");
					return;
				}
			}
		out.print("Yes");
	}

	public static void main(String[] args){new B913().run();}
	
	private byte[] bufferArray = new byte[1024];
	private int bufLength = 0;
	private int bufCurrent = 0;
	InputStream inputStream;
	PrintWriter out;
	
	public void run()
	{
		inputStream = System.in;
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}
	
	int nextByte()
	{
		if(bufLength == -1)
			throw new InputMismatchException();
		if(bufCurrent >= bufLength)
		{
			bufCurrent = 0;
			try
			{bufLength = inputStream.read(bufferArray);}
			catch(IOException e)
			{ throw new InputMismatchException();}
			if(bufLength <= 0)
				return -1;
		}
		return bufferArray[bufCurrent++];
	}
	
	boolean isSpaceChar(int x)	{return (x < 33 || x > 126);}
	
	boolean isDigit(int x)	{return (x >= '0' && x <= '9');}
	
	int nextNonSpace()
	{
		int x;
		while((x=nextByte()) != -1 && isSpaceChar(x));
		return x;
	}
	
	int ni()
	{
		long ans = nl();
		if (ans >= Integer.MIN_VALUE && ans <= Integer.MAX_VALUE)
			return (int)ans;
		throw new InputMismatchException();
	}
	
	long nl()
	{
		long ans = 0;
		boolean neg = false;
		int x = nextNonSpace();
		if(x == '-') 
		{
			neg = true;
			x = nextByte();
		}
		while(!isSpaceChar(x))
		{
			if(isDigit(x))
			{
				ans = ans * 10 + x -'0';
				x = nextByte();
			}
			else
				throw new InputMismatchException();
		}
		return neg ? -ans : ans;
	}
	
	String ns()
	{
		StringBuilder sb = new StringBuilder();
		int x = nextNonSpace();
		while(!isSpaceChar(x))
		{
			sb.append((char)x);
			x = nextByte();
		}
		return sb.toString();
	}
	
	char nc()	{ return (char)nextNonSpace();}
	
	double nd()	{ return (double)Double.parseDouble(ns()); }
	
	char[] ca()	{ return ns().toCharArray();}
	
	char[][] ca(int n)
	{
		char[][] ans = new char[n][];
		for(int i=0;i<n;i++)
			ans[i] = ca();
		return ans;
	}
	
	int[] ia(int n)
	{
		int[] ans = new int[n];
		for(int i=0;i<n;i++)
			ans[i] = ni();
		return ans;
	}
	
	void db(Object... o) {System.out.println(Arrays.deepToString(o));}
	
}