P2152 [SDOI2009] SuperGCD

Sheng bill has amazing mental arithmetic skills and can even compute the greatest common divisor of two huge numbers in his head. Therefore, he often competes with others in computing the greatest common divisor. One day, Sheng bill arrogantly challenged you, but losing to Sheng bill would be embarrassing. So you decide to write a program to teach him a lesson.

Two lines: the first line contains an integer $a$, and the second line contains an integer $b$.

One line, representing the greatest common divisor of $a$ and $b$.

#### Constraints - For $20\%$ of the testdata, $0