Keven#8495
Consider a string of even length and an integer . The string is called -even if and only if the first half of the string differs from the second half in no more than positions.
For example, the string is -even, -even, but not -even.
You are given an integer and a cyclic string of odd length. You are to find its -even substring of maximal length. Note that the input string is cyclic, so you can use any of its cyclic shifts.
The first line contains the integer (0 \leq k \leq 2000). The second line contains a string consisting of uppercase Latin letters. The length of the string is odd and does not exceed .
Print a single line containing the -even substring of maximal length. If there are several such substrings, print the smallest in lexicographical order. If such a substring does not exist, print a blank line.
Example 1
Example 2
Example 3