There are 20 socks of red, black and white in a cloth bag, the minimum number of socks must be taken to ensure that there are at least 2 pairs of socks of the same color.
一个布袋里有红、黑、白三种颜色的袜子各20只，最少要拿多少只，才能保证其中至少有2双颜色相同的袜子．
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

<result>6</result>