Problem Statement

You are given a string str consisting of English lowercase alphabets only. Let brr be another string that is made by first taking all the even indexed characters of the str and then the odd indexed character of str$.$

Your task is to find the first non$-$repeating character in brr$.$

Note:

If no character is non$-$repeating, print $"-1"$;

Input Format

The first and only line contains a single string str$.$

Output Format

Print the first non$-$repeating character of the string brr$.$

Constraints:

$0|str|{10}^{{?}^{{?}^{?}}}5$

${?}^{\text{'}\text{'}}str[i]{?}^{\text{'}}{z}^{\text{'}}$