#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9 + 10, MAX = 2e5 + 1e4, MOD = 1e9 + 7, MAXL = 25;
void OUT(long double o, int x) {
  cout << fixed << setprecision(x) << o;
  return;
}
long long a[MAX], t = 1;
vector<int> adj[MAX];
void dfs(int v, int p) {
  long long c = 0;
  for (int u : adj[v]) {
    if (u != p) {
      dfs(u, v);
      if (adj[u].size() == 1) c++;
    }
  }
  if (adj[v].size() > 1 && c < 3) t = 0;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  for (int i = 2; i <= n; i++) {
    long long x;
    cin >> x;
    adj[x].push_back(i);
    adj[i].push_back(x);
  }
  dfs(1, 1);
  if (t)
    cout << "Yes";
  else
    cout << "No";
  return 0;
}

### Prompt

In CPP, your task is to solve 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;
const long long INF = 1e9 + 10, MAX = 2e5 + 1e4, MOD = 1e9 + 7, MAXL = 25;
void OUT(long double o, int x) {
  cout << fixed << setprecision(x) << o;
  return;
}
long long a[MAX], t = 1;
vector<int> adj[MAX];
void dfs(int v, int p) {
  long long c = 0;
  for (int u : adj[v]) {
    if (u != p) {
      dfs(u, v);
      if (adj[u].size() == 1) c++;
    }
  }
  if (adj[v].size() > 1 && c < 3) t = 0;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  for (int i = 2; i <= n; i++) {
    long long x;
    cin >> x;
    adj[x].push_back(i);
    adj[i].push_back(x);
  }
  dfs(1, 1);
  if (t)
    cout << "Yes";
  else
    cout << "No";
  return 0;
}

```