Score : $100$ points

问题描述

你将得到一个长度为 $3$ 的字符串 $S$。 请输出在 $S$ 中只出现一次的字符(第一个）。 如果不存在这样的字符，则输出 -1。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

You are given a string $S$ of length $3$. Print a character that occurs only once in $S$. If there is no such character, print -1 instead.

Constraints

• $S$ is a string of length $3$ consisting of lowercase English letters.

Input

Input is given from Standard Input in the following format:

$S$

Output

Print the answer. If multiple solutions exist, you may print any of them.

Sample Input 1

pop

Sample Output 1

o

o occurs only once in pop.

Sample Input 2

abc

Sample Output 2

a

a, b, and c occur once each in abc, so you may print any of them.

Sample Input 3

xxx

Sample Output 3

-1

No character occurs only once in xxx.

update @ 2024/3/10 11:00:46