It's been quite a number of years since Lich Sandro retired. Sometimes in the evenings, when he feels especially lonely, he takes a book that was presented to him by his student magicians on the occasion of his retirement.
This evening the great magician is also reading the book. One of the chapters describes Sandro's famous discovery: he invented a universal spell many years ago. Any substring (a few consecutive symbols of the string) of the universal spell is also a spell, and its power is equal to the number of times this spell is encountered in the universal spell (for example, the string “ue” encounters in the string “queue” twice, and the string “aba” encounters in the string “abababa” three times).
Sandro has a lot of free time now and he wants to find the most powerful spell.
Help Sandro do it.
The only input line contains the universal spell invented by Sandro. The spell is a non-empty string consisting of lowercase English letters with length at most 50.
Output any of the most powerful spells, according to Sandro's definition.
Problem Author: Ivan Burmistrov (prepared by Olga Soboleva)
Problem Source: Ural Regional School Programming Contest 2009