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 CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
bool spruce(int n, int children[][1000], int numOfChildren[]) {
  for (int i = 0; i < n; i++) {
    int leafKids = 0;
    for (int j = 0; j < numOfChildren[i]; j++) {
      if (numOfChildren[children[i][j]] == 0) leafKids++;
    }
    if (numOfChildren[i] > 0 && leafKids < 3) return false;
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  int children[n][1000], numOfChildren[n];
  for (int i = 0; i < n; i++) numOfChildren[i] = 0;
  for (int i = 1; i < n; i++) {
    int parent;
    cin >> parent;
    parent--;
    children[parent][numOfChildren[parent]] = i;
    numOfChildren[parent]++;
  }
  if (spruce(n, children, numOfChildren))
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}