There are 10 identical balls numbered 1, 2, 3, 4, and 5 in a box, at least how many balls must be taken out to ensure that there are at least 2 balls with the same number.
一个箱子里有编号为1、2、3、4、5的相同小球各10个，至少要取出多少个小球才能保证其中至少有2个号码相同的小球．
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<result>6</result>