There are 3 keys and 3 locks. I don’t know which key matches which lock. How many times can I open 3 locks at most?
3把钥匙3把锁，不知道哪把钥匙配哪把锁，最多试开多少次可以保证打开3把锁．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>