The sum of three consecutive odd numbers is 645. What is the smallest odd number among these three odd numbers?
三个连续奇数的和是645．这三个奇数中，最小的奇数是多少．
<gadget id="calculator">645 / 3</gadget>
<output>215</output>

<gadget id="calculator">215 - 2</gadget>
<output>213</output>

<result>213</result>