B'You are given a string s of length n . Each character is either one of the first k lowercase Latin letters or a question mark. You are asked to replace every question mark with one of the first k lowercase Latin letters in such a way that the following value is maximized. Let f_i be the maximum length substring of string s , which consists entirely of the i -th Latin letter. A substring of a string is a contiguous subsequence of that string. If the i -th letter doesn 't appear in a string, then f_i is equal to 0 . The value of a string s is the minimum value among f_i for all i from 1 to k . What is the maximum value the string can have? The first line contains two integers n and k ( 1 <= n <= 2 cdot 10^5 ; 1 <= k <= 17 ) -- the length of the string and the number of first Latin letters used. The second line contains a string s , consisting of n characters. Each character is either one of the first k lowercase Latin letters or a question mark. Print a single integer -- the maximum value of the string after every question mark is replaced with one of the first k lowercase Latin letters. In the first example the question marks can be replaced in the following way: "aaaababbbb". f_1 = 4 , f_2 = 4 , thus the answer is 4 . Replacing it like this is also possible: "aaaabbbbbb". That way f_1 = 4 , f_2 = 6 , however, the minimum of them is still 4 . In the second example one of the possible strings is "aabbccdda". In the third example at least one letter won 't appear in the string, thus, the minimum of values f_i is always 0 . '...