PROGRAMMING:Find the first character that appears only once
###Task description
Given a string containing only lowercase letters, please find the first character that appears only once. If not, output No.
###Input format:
A string less than 100000 in length.
###Output format:
Output the first character that appears only once, if not, output No.
###Input example:
```in
abcabd
```
###Output example:
```out
c
```
###Title Source
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0107/02/
answer：If there is no answer, please comment
Given a string containing only lowercase letters, please find the first character that appears only once. If not, output No.
###Input format:
A string less than 100000 in length.
###Output format:
Output the first character that appears only once, if not, output No.
###Input example:
```in
abcabd
```
###Output example:
```out
c
```
###Title Source
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0107/02/
answer：If there is no answer, please comment