\includegraphics{https://static.e-olymp.com/content/4b/4bde6fe5e3c76d5cbc101c3dc47c3c1d8815682b.gif} The endpoints of the segment have integer coordinates. Count the number of points on the segment with integer coordinates. \InputFile Four integers represent the coordinates $x_1, y_1, x_2, y_2$ of the endpoints of the segment. The coordinate values do not exceed $2 \cdot 10^9$ in absolute value. \OutputFile Print the number of points on the segment with integer coordinates.