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 JAVA):

Solution:
import java.util.*;

public class codeforces {

    public codeforces() {
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        codeforces tree = new codeforces();
        int n = sc.nextInt();
        int[] m = new int[n-1];
        int[] p = new int[n];
        for (int i = 0; i < n-1; i++) {
            m[i] = sc.nextInt();
        }

        int j = 0;
        for (int i = 0; i < n-1; i++) {
            p[m[i]-1]++;
        }

        String message = "Yes";
        loop:
        for (int i = 0; i < n; i++) {
            int count = 0;
            if(p[i] == 0) continue;
            for (int k = 0; k < n - 1; k++) {
                if(m[k] == i+1 && p[k+1] == 0) {
                    count++;
                }
                if(k == n - 2 && count >= 0 && count < 3) {
                    message = "No";
                    break loop;
                }
            }
        }

        System.out.println(message);
    }

    public void printArray(int[] p) {
        for (int i = 0; i < p.length; i++) {
            System.out.print(p[i] + " ");
        }
    }

}