The sum of seven consecutive natural numbers is 105, what is the smallest number among them?
七个连续自然数的和是105，其中最小的数是多少．
<gadget id="calculator">105 / 7</gadget>
<output>15</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>