Problem Statement
There is a tree with $N$ vertices numbered from $1$ to $N$, where the $i$-th edge connects vertices $A_i$ and $B_i$.
We will now randomly write real numbers between $-(N-1)$ and $1$ (inclusive) on each vertex of this tree. The random number distributions are all independent uniform distributions.
Then, the score of the tree is defined as follows:
- For each vertex
$i$, define$x_i$as follows: - The maximum value of the sum of values written on vertices of connected subgraphs that contain vertex
$i$ - If there exists
$i$that does not satisfy$0 \leq x_i \leq 1$, the tree's score is$0$. - Otherwise, the tree's score is
$\prod_{1 \leq i \leq N} x_i$.
Find the expected value $\text{mod }{998244353}$ of the tree's score.
Definition of expected value $\text{mod }{998244353}$ It can be proved that the sought expected value is always a rational number. Also, under the constraints of this problem, it can be proved that when the value is expressed as an irreducible fraction $\frac{P}{Q}$, we have $Q \neq 0 \pmod{998244353}$. Therefore, an integer $R$ satisfying $R \times Q \equiv P \pmod{998244353}, 0 \leq R < 998244353$ is uniquely determined. Answer this $R$.
Constraints
$1 \leq N \leq 5000$$1 \leq A_i, B_i \leq N$- The input graph is a tree.
Input
The input is given from Standard Input in the following format:
N
A_1 B_1
A_2 B_2
\vdots
A_{N-1} B_{N-1}
Output
Output the answer.
样例
1
499122177
2
1 2
873463809
3
1 2
2 3
842653798
5
1 2
2 3
3 4
4 5
132050425
8
1 2
1 3
1 4
1 5
5 6
5 7
5 8
243711918
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