One key opens one lock. Now there are 4 keys and 4 locks. How many times can you determine which key belongs to which lock?
一把钥匙开一把锁，现在有4把钥匙4把锁，最多开多少次可以确定哪把钥匙属于哪把锁？
<gadget id="calculator">3 + 2 + 1</gadget>
<output>6</output>

<result>6</result>