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())
num_child = [0] * n
leaf_children = [0]*n
parents = []
ans = "Yes"

for i in range(n-1):
    # take in the input - append the parent of each node [i] to array parents[]
    parent_node = int(input())
    parents.append(parent_node)
    # add 1 to the the parents index (i) in num_children for each child added in parents array
    num_child[parent_node - 1] += 1

#
for i in range(n-1):
    c = parents[i]
    leaf_children[c-1] += {True: 1, False: 0}[num_child[i + 1] == 0]

for i in range(n):
    if num_child[i] > 0 and leaf_children[i] < 3:
        ans = "No"
print(ans)