\BOOKMARK [1][-]{section.1}{Introduction}{}% 1
\BOOKMARK [1][-]{section.2}{Regular chessboards}{}% 2
\BOOKMARK [1][-]{section.3}{Cylindrical chessboards}{}% 3
\BOOKMARK [1][-]{section.4}{Concluding remarks}{}% 4
\BOOKMARK [1][-]{section.5}{Acknowledgments}{}% 5