102600: [AtCoder]ABC260 A - A Unique Letter

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.

问题描述

给你一个长度为3的字符串$S$。
打印在$S$中只出现一次的字符。
如果没有这样的字符，打印-1代替。

限制条件

• $S$是一个长度为3的字符串，由小写英文字母组成。

输入

输入从标准输入以以下格式给出：

$S$

输出

打印答案。如果存在多个解，你可以打印其中任何一个。

样例输入1

pop

样例输出1

o

o在pop中只出现一次。

样例输入2

abc

样例输出2

a

a，b和c在abc中各出现一次，所以你可以打印其中任何一个。

样例输入3

xxx

样例输出3

-1

xxx中没有只出现一次的字符。