The sum of 5 consecutive natural numbers is 45, what is the smallest number among them.
5个连续的自然数之和为45，其中最小的数是多少．
<gadget id="calculator">45 / 5</gadget>
<output>9</output>

<gadget id="calculator">9 - 2</gadget>
<output>7</output>

<result>7</result>