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5105: LCS Again

内存限制：256 MB 时间限制：2 S
题面：传统 评测方式：文本比较 上传者：
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题目描述

D. LCS Again
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
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.
Input
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.
Output
Print the only line containing the answer.
Examples
Input 
3 3
aaa
Output 
6
Input 
3 3
aab
Output 
11
Input 
1 2
a
Output 
1
Input 
10 9
abacadefgh
Output 
789
Note
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.

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