There are 10 red, blue, yellow and green balls of the same size in a box. There must be 2 balls of the same color if you want to draw out the balls, at least how many balls must be drawn out.
盒子里有大小一样的红球、蓝球、黄球和绿球各10个．要想摸出的球一定有2个同色的，最少要摸出多少个球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>