One key opens one lock. There are 5 keys and 5 locks, but they don’t know how to match them. How many times do you have to try to ensure that they match the locks?
一把钥匙开一把锁，现有5把钥匙和5把锁，但不知怎么相配，最多要试多少次才能确保和锁相配．
<gadget id="calculator">4 + 3 + 2 + 1</gadget>
<output>10</output>

<result>10</result>