The sum of 3 consecutive odd numbers is 57, what is the smallest number among these three numbers?
3个连续奇数的和是57，这三个数中最小的那个数是多少．
<gadget id="calculator">57 / 3</gadget>
<output>19</output>

<gadget id="calculator">19 - 2</gadget>
<output>17</output>

<result>17</result>