PROGRAMMING:*Finding the greatest common divisor

Please write a program, input two integers, calculate and output their greatest common divisor.
####Input format
>Two integers
####Output format
>Greatest common divisor (positive integer)
Note: two integers can be positive, zero and negative, and the number of digits of both integers is less than 20. The greatest common divisor must be a positive integer.
Note: if both integers are 0, the greatest common divisor is 1.
####Input sample 1
```in
25 30
```
####Output sample 1
```out
five
```
####Input sample 2
```in
7 0
```
####Output sample 2
```out
seven
```
####Input sample 3
```in
0 0
```
####Output sample 3
```out
one
```







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