A's number is 15, which is 1 less than twice the number that has been counted. What is the number that has been counted?
甲数是15，比已数的2倍少1，已数是多少．
<gadget id="calculator">15 + 1</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>