AT_abc428_b [ABC428B] Most Frequent Substrings

You are given a string $ S $ of length $ N $ consisting of lowercase English letters. Define the **number of occurrences** of a string $ t $ of length $ K $ as the number of integers $ i $ that satisfy the following condition: - $ 1 \leq i \leq N-K+1 $ - The substring of $ S $ from the $ i $ -th character to the $ (i+K-1) $ -th character matches $ t $ . Find the maximum value $ x $ of the number of occurrences of a string of length $ K $ . Also, output all strings of length $ K $ with $ x $ occurrences in ascending lexicographical order.

The input is given from Standard Input in the following format: > $ N $ $ K $ $ S $

Output two lines. The first line should contain the maximum value $ x $ of the number of occurrences of a string of length $ K $ . The second line should contain all strings of length $ K $ with $ x $ occurrences in ascending lexicographical order, separated by spaces.

### Sample Explanation 1 The following strings have two occurrences: - For the string `ovo`, $ i=1,7 $ satisfy the condition, so the number of occurrences of `ovo` is $ 2 $ . - For the string `owo`, $ i=3,5 $ satisfy the condition, so the number of occurrences of `owo` is $ 2 $ . There is no string of length $ 3 $ with more than two occurrences, so the maximum value is $ 2 $ . On the other hand, the following are examples of strings with fewer than two occurrences: - For the string `vow`, $ i=2 $ satisfies the condition, so the number of occurrences of `vow` is $ 1 $ . - For the string `ooo`, there is no $ i $ that satisfies the condition, so the number of occurrences of `ooo` is $ 0 $ . ### Constraints - $ N, K $ are integers. - $ S $ is a string of length $ N $ consisting of lowercase English letters. - $ 1 \leq K \leq N \leq 100 $