PROGRAMMING:greatest common factor
Find the greatest common divisor of two integers.
###Input format:
Enter two integers separated by spaces.
###Output format:
Output the greatest common divisor.
###Input example:
```in
9 18
```
###Output example:
```out
nine
```
answer：If there is no answer, please comment
###Input format:
Enter two integers separated by spaces.
###Output format:
Output the greatest common divisor.
###Input example:
```in
9 18
```
###Output example:
```out
nine
```
answer：If there is no answer, please comment