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 PYTHON3):

Solution:
n = int(input().strip())
parents = [0]*(n+1)
for i in range(2, n+1):
	parent = int(input().strip())
	parents[i] = parent
tree = {}

for i in range(1, n+1):
	tree[i] = []

for node in range(1, n+1):
	for i in range(2, len(parents)):
		if parents[i] == node:
			tree[node].append(i)

for node in range(1, n+1):
	if len(tree[node]) != 0:
		leaf_childs = 0
		for child in tree[node]:
			if len(tree[child]) == 0:
				leaf_childs += 1
		if leaf_childs < 3:
			print('No')
			quit()
print('Yes')