There are 5 red balls and 5 blue balls in the bag. If you want to take out two balls of the same color from the bag at one time, how many balls must you take out at least.
袋子中有红、蓝球各5个，如果要保证一次能从布袋中取出两个相同颜色的球，至少必须取出多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>