$\displaystyle \frac{1}{6}$\displaystyle \frac{1}{6}

$\displaystyle \frac{1}{12}$\displaystyle \frac{1}{12}

$\displaystyle \frac{1}{18}$\displaystyle \frac{1}{18}

$\displaystyle \frac{1}{36}$\displaystyle \frac{1}{36}