Isomorphisms#5910
Two strings and are called isomorphic if all letters of the first string can be renamed so as to obtain the second string. Different letters must be renamed to different letters, and identical letters to identical ones.
For example, the strings "" and "" are isomorphic. A valid renaming is: replace letter '' with '' and letter '' with ''. The strings "" and "" are not isomorphic.
You are given a string . Define the function (where is a non-empty string) as the number of substrings of that are isomorphic to , multiplied by the length of . Your task is to find a string , consisting of lowercase Latin letters, such that the value of is maximized.
The first line contains the string (1 \leq |s| \leq 2000), consisting of lowercase Latin letters.
Output an optimal string . If there are multiple such strings, output any. The output string must consist of lowercase Latin letters.
Example 1