\BOOKMARK [1][-]{section.1}{1. Introduction}{}
\BOOKMARK [1][-]{section.2}{2. The natural numbers}{}
\BOOKMARK [1][-]{section.3}{3. The integers}{}
\BOOKMARK [1][-]{section.4}{4. The rational numbers}{}
\BOOKMARK [1][-]{section.5}{5. Periodic decimal expansion of rational numbers}{}
\BOOKMARK [1][-]{section.6}{6. Functions}{}