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 PYTHON):

Solution:
n = input()
nleaf = [0 for i in xrange(n)]
chil = [[] for i in xrange(n)]
for i in xrange(n-1):
	x = input()
	nleaf[x-1] = 1
	chil[x-1].append(i+1)
f = 0
#print nleaf
#print chil
for i in xrange(n):
	cnt = 0
	l = len(chil[i])
	if nleaf[i] == 1:
		for j in xrange(l):
			if nleaf[chil[i][j]] == 0:
				cnt += 1
			if cnt == 3:
				break
		if cnt < 3:
			f = 1
			break
if f == 1:
	print 'No'
else:
	print 'Yes'