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;
int n, cnt, ans;
int SZ[1005];
vector<int> gg[1005];
bool dfs(int now, int pre) {
  int sz = gg[now].size(), tt = 0;
  for (int i = 0; i < sz; i++) {
    int nex = gg[now][i];
    if (nex == pre) continue;
    if (gg[nex].size() == 1) tt++;
  }
  if (tt < 3) return 0;
  for (int i = 0; i < sz; i++) {
    int nex = gg[now][i];
    if (nex == pre) continue;
    if (gg[nex].size() != 1)
      if (!dfs(nex, now)) return 0;
  }
  return 1;
}
int main() {
  scanf("%d", &n);
  for (int i = 2; i <= n; i++) {
    int a;
    scanf("%d", &a);
    gg[a].push_back(i);
    gg[i].push_back(a);
  }
  if (dfs(1, -1))
    printf("Yes\n");
  else
    printf("No\n");
  return 0;
}