# Power of String

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#
#   For a given integer K and a string S of length N, we denote power of S, as the length of a longest substring
#   occurring in S at least K times. Given K and S, find the power of S.
#
#   Constraints:
#   1 <= N <= 10^6
#   1 <= K <= N
#   S consists of latin lowercase letters only
#
#   Input format:
#   In the first line there are two integers K and N separated by a single space.
#   The second line constains string S itself.
#
#   Output format:
#   In one line, output the power of string S for a given K.
#
#   SAMPLE INPUT
#   2 11
#   abrakadabra
#
#   SAMPLE OUTPUT
#   4
#
#   Explanation
#   Substring "abra" occurs in S two times and
#   it is the longest substring of all substrings of S occurring at least two times.
#
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