The keys of 30 locks in the male dormitory of Xinghe International School were messed up. In order to make each lock match its own key, how many times would it take at most.
兴合国际学校男生宿舍共有30把锁的钥匙搞乱了，为了使每把锁都配上自己的钥匙，至多要试多少次．
<gadget id="calculator">29 + 1</gadget>
<output>30</output>

<gadget id="calculator">29 / 2</gadget>
<output>29/2 = around 14.5</output>

<gadget id="calculator">30 * (29/2)</gadget>
<output>435</output>

<result>435</result>