From a total of 16 integers from 1 to 16, at least how many numbers can be taken to ensure that there are two numbers, one of which is twice the other.
从1至16共16个整数中，至少取多少个数，才能确保有两个数，其中一个是另一个的2倍．
<gadget id="calculator">11 + 1</gadget>
<output>12</output>

<result>12</result>