cloth bag contains 20 red, yellow and black socks each. How many socks must be taken at least to ensure that there are at least 2 pairs of socks with different colors.
一个布袋里有红色、黄色、黑色袜子各20只．最少要拿多少只袜子才能保证其中至少有2双颜色不相同的袜子．
<gadget id="calculator">20 + 2 + 1</gadget>
<output>23</output>

<result>23</result>