P24316 [AtCoder] typewriter
提高-
题目描述

Problem Statement

We have a typewriter with N rows. The keys in the i-th row from the top can type the characters in a string S_i.
Let us use this keyboard to enter a string, as follows.

  • First, choose an integer $1 \le k \le N$.
  • Then, start with an empty string and only use the keys in the k-th row from the top to enter a string of length exactly L.

How many strings of length L can be entered in this way?
Since the answer can be enormous, print it modulo 998244353.

Input

Input is given from Standard Input in the following format:
N L
S_1
S_2
$\dots$
S_N

Output

Print the answer.

Constraints

  • N and L are integers.
  • $1 \le N \le 18$
  • $1 \le L \le 10^9$
  • S_i is a (not necessarily contiguous) non-empty subsequence of abcdefghijklmnopqrstuvwxyz.

Sample Input 1

2 2
ab
ac

Sample Output 1

7

We can enter seven strings: aa, ab, ac, ba, bb, ca, cc.

Sample Input 2

4 3
abcdefg
hijklmnop
qrstuv
wxyz

Sample Output 2

1352

Sample Input 3

5 1000000000
abc
acde
cefg
abcfh
dghi

Sample Output 3

346462871

Be sure to print the answer modulo 998244353.

输入格式

见题面 Input 部分

输出格式

见题面 Output 部分

样例输入
2 2 ab ac
样例输出
7