You are given a string. Find it's longest palindromic substring.

Input

The only input line contains a string of length $n$. Each character is one of a–z.

Output

Print the longest palindrome in the string. If there are several solutions, you may print any of them.

Constraints

• $1 \le n \le 10^6$

Example 1

Input:

aybabtu

Output:

bab

Example 2

Input:

asdfsaippuakauppiasasdf

Output:

saippuakauppias