There are 10 black socks, 10 white socks, and 10 yellow socks. Take out random socks without looking at them with your eyes, so that at least two pairs of socks are of different colors. Then at least how many socks should be taken out.
有黑、白、黄色袜子各10只，不用眼睛看，任意地取出袜子来，使得至少有两双袜子不同色，那么至少要取出多少只袜子．
<gadget id="calculator">10 + 2 + 1</gadget>
<output>13</output>

<result>13</result>