Teacher Liu wants to buy some notebooks as prizes, 9 yuan for each large notebook and 6 yuan for each small notebook. If you buy all the small books, there will be 2 yuan left; if you buy all the big books, there will be 2 yuan left. How much money did Mr. Liu bring at least?
刘老师要买一些笔记本作为奖品，大本每本9元，小本每本6元．如果都买小本的，还剩2元；如果都买大本的，也剩2元，刘老师至少带了多少钱？
<gadget id="calculator">2 * 3 * 3</gadget>
<output>18</output>

<gadget id="calculator">18 + 2</gadget>
<output>20</output>

<result>20</result>