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:

def do_it(trees):
    import collections
    a = collections.defaultdict(list)
    non_leaf = collections.defaultdict(int)
    for i in xrange(len(trees)):
        a[trees[i]].append(i+2)
        non_leaf[trees[i]] = 1

    for tr in a:
        tem_sum = 0
        for val in a[tr]:
            tem_sum += non_leaf[val]
        number_of_child_leaf = len(a[tr])-tem_sum
        if number_of_child_leaf <3: return "No"
    return "Yes"
    
n = int(raw_input())
trees = []
for i in range(n-1):
   trees.append(int(raw_input()))
print do_it(trees)