PROGRAMMING:Case conversion
Case conversion.
###Input format:
Input several English letters to the end of the file.
###Output format:
If the input English letter is uppercase, it will be converted to lowercase, otherwise it will be converted to uppercase.
###Input example:
Here is a set of inputs. For example:
```in
A
b
```
###Output example:
The corresponding output is given here. For example:
```out
a
B
```
answer：If there is no answer, please comment
###Input format:
Input several English letters to the end of the file.
###Output format:
If the input English letter is uppercase, it will be converted to lowercase, otherwise it will be converted to uppercase.
###Input example:
Here is a set of inputs. For example:
```in
A
b
```
###Output example:
The corresponding output is given here. For example:
```out
a
B
```
answer：If there is no answer, please comment