There are 10 locks, each with a key. Xiao Ming accidentally messed up the keys of 10 locks. In order to match the 10 locks with suitable keys, how many times must he try at least?
有10把锁，每把锁都配有一把钥匙．小明不小心把10把锁的钥匙搞乱了，为了使10把锁配上合适的钥匙，至少要试多少次．
<gadget id="calculator">9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>45</output>

<result>45</result>