#D11115. tree
tree
tree
Let F_k denote the k-th term of Fibonacci sequence, defined as below:
- F_0 = F_1 = 1
- for any integer n ≥ 0, F_{n+2} = F_{n+1} + F_n
You are given a tree with n vertices. Recall that a tree is a connected undirected graph without cycles.
We call a tree a Fib-tree, if its number of vertices equals F_k for some k, and at least one of the following conditions holds:
- The tree consists of only 1 vertex;
- You can divide it into two Fib-trees by removing some edge of the tree.
Determine whether the given tree is a Fib-tree or not.
Input
The first line of the input contains a single integer n (1 ≤ n ≤ 2 ⋅ 10^5) — the number of vertices in the tree.
Then n-1 lines follow, each of which contains two integers u and v (1≤ u,v ≤ n, u ≠ v), representing an edge between vertices u and v. It's guaranteed that given edges form a tree.
Output
Print "YES" if the given tree is a Fib-tree, or "NO" otherwise.
You can print your answer in any case. For example, if the answer is "YES", then the output "Yes" or "yeS" will also be considered as correct answer.
Examples
Input
3 1 2 2 3
Output
YES
Input
5 1 2 1 3 1 4 1 5
Output
NO
Input
5 1 3 1 2 4 5 3 4
Output
YES
Note
In the first sample, we can cut the edge (1, 2), and the tree will be split into 2 trees of sizes 1 and 2 correspondently. Any tree of size 2 is a Fib-tree, as it can be split into 2 trees of size 1.
In the second sample, no matter what edge we cut, the tree will be split into 2 trees of sizes 1 and 4. As 4 isn't F_k for any k, it's not Fib-tree.
In the third sample, here is one possible order of cutting the edges so that all the trees in the process are Fib-trees: (1, 3), (1, 2), (4, 5), (3, 4).
inputFormat
Input
The first line of the input contains a single integer n (1 ≤ n ≤ 2 ⋅ 10^5) — the number of vertices in the tree.
Then n-1 lines follow, each of which contains two integers u and v (1≤ u,v ≤ n, u ≠ v), representing an edge between vertices u and v. It's guaranteed that given edges form a tree.
outputFormat
Output
Print "YES" if the given tree is a Fib-tree, or "NO" otherwise.
You can print your answer in any case. For example, if the answer is "YES", then the output "Yes" or "yeS" will also be considered as correct answer.
Examples
Input
3 1 2 2 3
Output
YES
Input
5 1 2 1 3 1 4 1 5
Output
NO
Input
5 1 3 1 2 4 5 3 4
Output
YES
Note
In the first sample, we can cut the edge (1, 2), and the tree will be split into 2 trees of sizes 1 and 2 correspondently. Any tree of size 2 is a Fib-tree, as it can be split into 2 trees of size 1.
In the second sample, no matter what edge we cut, the tree will be split into 2 trees of sizes 1 and 4. As 4 isn't F_k for any k, it's not Fib-tree.
In the third sample, here is one possible order of cutting the edges so that all the trees in the process are Fib-trees: (1, 3), (1, 2), (4, 5), (3, 4).
样例
3
1 2
2 3
YES
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