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;
void Read(int &x, char c = getchar(), bool f = 0) {
  for (x = 0; !isdigit(c); c = getchar())
    if (c == '-') f = 1;
  for (; isdigit(c); c = getchar()) x = 10 * x + c - '0';
  if (f) x = -x;
}
const int maxn = 2005;
int n, m;
int deg[maxn];
int fa[maxn];
bool nf[maxn];
int main() {
  Read(n);
  int i;
  for (i = 2; i <= n; i++) Read(fa[i]), nf[fa[i]] |= 1;
  for (i = 1; i <= n; i++)
    if (!nf[i]) ++deg[fa[i]];
  bool ok = 1;
  for (i = 1; i <= n; i++)
    if (nf[i] && deg[i] < 3) {
      ok = 0;
      break;
    }
  if (ok)
    puts("Yes");
  else
    puts("No");
  return 0;
}