One key unlocks one lock, now there are 8 keys and 8 locks messed up, how many times do you want to re-pair them at most?
一个钥匙开一把锁，现在有8把钥匙和8把锁被搞乱了，要把它们重新配对，最多试多少次．
<gadget id="calculator">7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>28</output>

<result>28</result>