\[\begin{array}[]{rl}\mbox{for $q>0$:}&a_{0}<b_{1}<a_{1}<b_{2}<a_{2}<b_{3}<%
\cdots,\\
\mbox{for $q<0$:}&a_{0}<a_{1}<b_{1}<b_{2}<a_{2}<a_{3}<\cdots.\end{array}\]