atcoder#ABC246F. [ABC246F] typewriter

[ABC246F] typewriter

Score : 500500 points

Problem Statement

We have a typewriter with NN rows. The keys in the ii-th row from the top can type the characters in a string SiS_i.

Let us use this keyboard to enter a string, as follows.

  • First, choose an integer 1kN1 \le k \le N.
  • Then, start with an empty string and only use the keys in the kk-th row from the top to enter a string of length exactly LL.

How many strings of length LL can be entered in this way? Since the answer can be enormous, print it modulo 998244353998244353.

Constraints

  • NN and LL are integers.
  • 1N181 \le N \le 18
  • 1L1091 \le L \le 10^9
  • SiS_i is a (not necessarily contiguous) non-empty subsequence of abcdefghijklmnopqrstuvwxyz.

Input

Input is given from Standard Input in the following format:

NN LL

S1S_1

S2S_2

\dots

SNS_N

Output

Print the answer.

2 2
ab
ac
7

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

4 3
abcdefg
hijklmnop
qrstuv
wxyz
1352
5 1000000000
abc
acde
cefg
abcfh
dghi
346462871

Be sure to print the answer modulo 998244353998244353.