6. In the magical town, you can only buy things with gems. In the town, 1 blue gem can be exchanged for 2 yellow gems, 3 yellow gems can be exchanged for 6 green gems, and 2 green gems can buy 7 lollipops. Xiao Bu has 1 blue gem and 2 yellow gems, she can buy $\qquad$ lollipops.
$28$