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())

parent = []
children = []
leaf = []
for i in range(N + 5):
  parent.append(0)
  children.append([])
  leaf.append(False)
for n in range(2, N + 1):
  parent[n] = int(input())
  children[parent[n]].append(n)

for n in range(1, N + 1):
  if len(children[n]) == 0 and parent[n]:
    leaf[n] = True

for n in range(1, N + 1):
  if not leaf[n]:
    cnt = 0
    for each in children[n]:
      cnt += leaf[each]
    if cnt < 3:
      print("No")
      quit()


print("Yes")