#include <bits/stdc++.h>
using namespace std;
long long vis[1005];
bool sortcol(const vector<long long>& v1, const vector<long long>& v2) {
  return v1[1] > v2[1];
}
vector<long long> adj[1002];
long long dfs(long long node) {
  if (adj[node].size() == 0) {
    return 1;
  }
  vis[node] = 1;
  long long cnt = 0;
  for (long long child : adj[node]) {
    if (vis[child] == 0) {
      if (adj[child].size() == 0) {
        cnt++;
      }
    }
  }
  if (cnt < 3) {
    return 0;
  }
  for (long long child : adj[node]) {
    if (vis[child] == 0) {
      if (dfs(child) == 0) return 0;
    }
  }
  return 1;
}
long long solve() {
  long long n;
  cin >> n;
  for (long long i = 1; i < n; i++) {
    long long l;
    cin >> l;
    adj[l].push_back(i + 1);
  }
  long long i = dfs(1);
  if (i)
    cout << "Yes";
  else {
    cout << "No";
  }
  return 0;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t;
  solve();
  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;
long long vis[1005];
bool sortcol(const vector<long long>& v1, const vector<long long>& v2) {
  return v1[1] > v2[1];
}
vector<long long> adj[1002];
long long dfs(long long node) {
  if (adj[node].size() == 0) {
    return 1;
  }
  vis[node] = 1;
  long long cnt = 0;
  for (long long child : adj[node]) {
    if (vis[child] == 0) {
      if (adj[child].size() == 0) {
        cnt++;
      }
    }
  }
  if (cnt < 3) {
    return 0;
  }
  for (long long child : adj[node]) {
    if (vis[child] == 0) {
      if (dfs(child) == 0) return 0;
    }
  }
  return 1;
}
long long solve() {
  long long n;
  cin >> n;
  for (long long i = 1; i < n; i++) {
    long long l;
    cin >> l;
    adj[l].push_back(i + 1);
  }
  long long i = dfs(1);
  if (i)
    cout << "Yes";
  else {
    cout << "No";
  }
  return 0;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t;
  solve();
  return 0;
}

```