Repeating Substring

• Time limit: 1.00 s
• Memory limit: 512 MB

A repeating substring is a substring that occurs in two (or more) locations in the string. Your task is to find the longest repeating substring in a given string.

Input

The only input line has a string of length $n$ that consists of characters a–z.

Output

Print the longest repeating substring. If there are several possibilities, you can print any of them. If there is no repeating substring, print $-1$.

Constraints

• $1 \le n \le 10^5$
  

Example

Input:
cabababc

Output:
abab