There are 10 socks in each of the four colors of red, yellow, blue, and purple with the same size and style in a bag. One person takes socks from the bag with his eyes closed. How many socks must be taken at least to ensure that there are 2 pairs of the same color? sock.
一个袋子里有大小、式样完全相同的红、黄、蓝、紫4种颜色的袜子各10只，一人闭着眼睛从袋子中取袜子，至少取多少只袜子，才能保证有2双颜色相同的袜子．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 + 1</gadget>
<output>13</output>

<result>13</result>