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;
vector<int> v[1010];
bool dfs(int i) {
  bool t = true;
  int cnt = 0;
  if (v[i].size()) {
    for (int j = 0; j < v[i].size(); j++) {
      if (v[v[i][j]].size() == 0)
        cnt++;
      else
        t &= dfs(v[i][j]);
    }
  }
  return t & !(v[i].size() && cnt < 3);
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n;
  ;
  cin >> n;
  for (int i = 2; i <= n; i++) {
    int x;
    cin >> x;
    v[x].push_back(i);
  }
  if (dfs(1))
    cout << "YES";
  else
    cout << "NO";
  return 0;
}