There are 12 dirty socks and 20 clean socks in Xiaoli's socks basket. On this day, he dazedly took socks from the basket, two at a time. If there are dirty socks, they will throw both of them on the ground, and then take them again from the basket. Then, how many times can he take it at least to ensure that he will get two clean socks.
小李的袜子筐里有12只脏袜子和20只干净袜子．这天，他迷迷糊糊地从筐中拿袜子，每次拿两只．如果其中有脏袜子就会把两只都扔到地上，然后从筐中重拿．那么，他至少拿多少次才能保证一定拿到两只干净的袜子．
<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<result>13</result>