The reciprocal of the sum of three consecutive natural numbers is (1/15), what is the smallest natural number among them.
三个连续自然数的和的倒数是(1/15)，其中最小的自然数是多少．
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15) / 3</gadget>
<output>5</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<result>4</result>