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;
const int maxn = 1003;
vector<int> g[maxn];
int n;
bool ans = 1;
bool dfs(int nod) {
  int aa = 0;
  for (auto x : g[nod]) {
    aa += dfs(x);
  }
  if (aa > 0 && aa < 3) ans = 0;
  if (aa == 0 && g[nod].size()) ans = 0;
  return (aa == 0);
}
int main() {
  if (0) {
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
  }
  cin >> n;
  for (int i = 1; i <= n - 1; i++) {
    int x;
    cin >> x;
    g[x].push_back(i + 1);
  }
  dfs(1);
  cout << ((ans == 1) ? "Yes" : "No");
  return 0;
}