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