P24167 [AtCoder] Safety Journey
普及+
题目描述

Problem Statement

The Republic of AtCoder has $N cities, called City 1, City 2, \ldots, City N$.
Initially, there was a bidirectional road between every pair of different cities, but M of these roads have become unusable due to deterioration over time. More specifically, for each $1\leq i \leq M$, the road connecting City U_i and City V_i has become unusable.
Takahashi will go for a K-day trip that starts and ends in City 1. Formally speaking, a K-day trip that starts and ends in City 1 is a sequence of $K+1 cities (A_0, A_1, \ldots, A_K)$ such that A_0=A_K=1 holds and for each $0\leq i\leq K-1, A_i$ and A_{i+1} are different and there is still a usable road connecting City A_i and City A_{i+1}.
Print the number of different K-day trips that start and end in City $1, modulo 998244353. Here, two K-day trips (A_0, A_1, \ldots, A_K)$ and $(B_0, B_1, \ldots, B_K)$ are said to be different when there exists an i such that $A_i\neq B_i$.

Input

Input is given from Standard Input in the following format:
N M K
U_1 V_1
:
U_M V_M

Output

Print the answer.

Constraints

  • $2 \leq N \leq 5000$
  • $0 \leq M \leq \min\left( \frac{N(N-1)}{2},5000 \right)$
  • $2 \leq K \leq 5000$
  • $1 \leq U_i<V_i \leq N$
  • All pairs (U_i, V_i) are pairwise distinct.
  • All values in input are integers.

Sample Input 1

3 1 4
2 3

Sample Output 1

4

There are four different trips as follows.

  • (1,2,1,2,1)
  • (1,2,1,3,1)
  • (1,3,1,2,1)
  • (1,3,1,3,1)

No other trip is valid, so we should print 4.

Sample Input 2

3 3 3
1 2
1 3
2 3

Sample Output 2

0

No road remains usable, so there is no valid trip.

Sample Input 3

5 3 100
1 2
4 5
2 3

Sample Output 3

428417047

输入格式

见题面 Input 部分

输出格式

见题面 Output 部分

样例输入
3 1 4 2 3
样例输出
4