key is matched with a lock, and the careless uncle confuses 5 keys with 5 locks. How many times can they be matched at most before the corresponding key and lock can be found?
一把钥匙配一把锁，粗心的叔叔把5把钥匙和5把锁搞混了，最多配多少次，才能找到相应的钥匙和锁．
<gadget id="calculator">4 + 3 + 2 + 1</gadget>
<output>10</output>

<result>10</result>