Superstring Counter
----------- -------

A superstring of a set of strings is a string containing
every member of the set (possibly with overlapping) as a
substring.  You have been asked to find the number of
superstrings with a given length of a given set of
substrings.  All strings consist of lower case letters.


Input
-----

For each test case, one line containing just `n m',
where n is the length of the superstring and m is the
number of substrings to be included in it, followed by
m lines, each containing nothing but one substring.
1 <= m <= 10, 1 <= n <= 40.  Substrings contain only
lower case letters.  The input ends with an end of file.


Output
------

For each test case, one line containing the number of
superstrings containing just n lower case letters.  The
input will be such that the output will be less than
2^31.


Sample Input
------ -----

4 2
ab
cd
3 1
aa


Sample Output
------ ------

2
51


File:	   supercounter.txt
Author:	   Bob Walton <walton@deas.harvard.edu>
Date:	   Wed Oct 15 09:27:16 EDT 2008

The authors have placed this file in the public domain;
they make no warranty and accept no liability for this
file.

RCS Info (may not be true date or author):

    $Author: walton $
    $Date: 2008/10/15 13:27:26 $
    $RCSfile: supercounter.txt,v $
    $Revision: 1.5 $