Rectangle Covered with Squares

Given a rectangle with integer sides $a$ and $b$, find the largest possible side length of identical squares such that the rectangle can be completely covered by these squares, with none of the squares extending beyond the boundaries of the rectangle.

\InputFileTwo natural numbers $a$ and $b$ (0 < a,\ b < 2\ 000\ 000\ 000).

\OutputFileOutput a single integer—the side length of the square.