CSES - Repeating Substring
  • Time limit: 1.00 s
  • Memory limit: 512 MB
Find the longest repeating substring in a 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