Put 10 equal-sized balls of red, orange, red, green, cyan, blue, and purple into the box, at least how many balls are taken to ensure that there are two of the same color.
把赤、橙、红、绿、青、蓝、紫七种颜色大小相等的球各10个放入盒子，至少取多少个才能保证有两个颜色相同．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<result>8</result>