LCS Again
题目描述
You are given a string S of length n with each character being one of the first m lowercase English letters.
Calculate how many different strings T of length n composed from the first m lowercase English letters exist such that the length of LCS (longest common subsequence) between S and T is n-1.
Recall that LCS of two strings S and T is the longest string C such that C both in S and T as a subsequence.
The first line contains two numbers n and m denoting the length of string S and number of first English lowercase characters forming the character set for strings (1≤n≤100000, 2≤m≤26).
The second line contains string S.
Print the only line containing the answer.
3 3
aaa
6
3 3
aab
11
1 2
a
1
10 9
abacadefgh
789
For the first sample, the 6 possible strings T are: aab, aac, aba, aca, baa, caa.
For the second sample, the 11 possible strings T are: aaa, aac, aba, abb, abc, aca, acb, baa, bab, caa, cab.
For the third sample, the only possible string T is b.
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 1085 题。保留原作者与原赛事署名。