#include <bits/stdc++.h>
using namespace std;
long long n, m;
vector<vector<int> > vv;
vector<bool> visited;
vector<int> leaf;
void dfsfs(int f, int s) {
  if (visited[s]) {
    return;
  }
  visited[s] = true;
  if (vv[s].size() == 0) {
    leaf[f]++;
  }
  for (auto u : vv[s]) {
    dfsfs(s, u);
  }
}
int main() {
  cin >> n;
  vv.resize(n);
  visited.resize(n);
  leaf.resize(n);
  for (int i = 1; i < n; i++) {
    cin >> m;
    m--;
    vv[m].push_back(i);
  }
  dfsfs(0, 0);
  for (int i = 0; i < n; i++) {
    if (vv[i].size() == 0 || leaf[i] >= 3) {
      continue;
    } else {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
}

### Prompt

Please formulate a Cpp solution to the following 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>

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
long long n, m;
vector<vector<int> > vv;
vector<bool> visited;
vector<int> leaf;
void dfsfs(int f, int s) {
  if (visited[s]) {
    return;
  }
  visited[s] = true;
  if (vv[s].size() == 0) {
    leaf[f]++;
  }
  for (auto u : vv[s]) {
    dfsfs(s, u);
  }
}
int main() {
  cin >> n;
  vv.resize(n);
  visited.resize(n);
  leaf.resize(n);
  for (int i = 1; i < n; i++) {
    cin >> m;
    m--;
    vv[m].push_back(i);
  }
  dfsfs(0, 0);
  for (int i = 0; i < n; i++) {
    if (vv[i].size() == 0 || leaf[i] >= 3) {
      continue;
    } else {
      cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
}

```