#include <bits/stdc++.h>
using namespace std;
vector<int> graph[1001];
bool BFS(int source) {
  int visited[1001];
  queue<int> Q;
  memset(visited, 0, sizeof(visited));
  Q.push(source);
  visited[source] = 1;
  while (!Q.empty()) {
    int u = Q.front();
    Q.pop();
    if (graph[u].size() == 0) continue;
    int nonleaf = 0;
    for (int i = 0; i < graph[u].size(); i++) {
      int v = graph[u][i];
      if (visited[v] == 0) {
        visited[v] = 1;
        Q.push(v);
        if (graph[v].size() == 0) nonleaf++;
      }
    }
    if (nonleaf < 3) return 0;
  }
  return 1;
}
int main() {
  int N;
  cin >> N;
  int x;
  for (int i = 2; i <= N; i++) {
    cin >> x;
    graph[x].push_back(i);
  }
  bool ans = BFS(1);
  if (ans == true)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}

### Prompt

Develop a solution in cpp to the problem described below:

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;
vector<int> graph[1001];
bool BFS(int source) {
  int visited[1001];
  queue<int> Q;
  memset(visited, 0, sizeof(visited));
  Q.push(source);
  visited[source] = 1;
  while (!Q.empty()) {
    int u = Q.front();
    Q.pop();
    if (graph[u].size() == 0) continue;
    int nonleaf = 0;
    for (int i = 0; i < graph[u].size(); i++) {
      int v = graph[u][i];
      if (visited[v] == 0) {
        visited[v] = 1;
        Q.push(v);
        if (graph[v].size() == 0) nonleaf++;
      }
    }
    if (nonleaf < 3) return 0;
  }
  return 1;
}
int main() {
  int N;
  cin >> N;
  int x;
  for (int i = 2; i <= N; i++) {
    cin >> x;
    graph[x].push_back(i);
  }
  bool ans = BFS(1);
  if (ans == true)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}

```