13. Big Ears Tutu and his good friend ZHUANG ZHUANG come to the convenience store together, where the price of lollipops is: 1 yuan for one, 4 yuan for five, and 7 yuan for nine. Tutu has enough money to buy a maximum of 11 lollipops, and ZHUANG ZHUANG has enough money to buy a maximum of 23 lollipops. So, ZHUANG ZHUANG has $\qquad$ more yuan than Tutu.
$9$