When two numbers are divided, the quotient is 21 and the remainder is 13. What is the smallest dividend?
两数相除，商21，余数为13，被除数最小为多少．
<gadget id="calculator">13 + 1</gadget>
<output>14</output>

<gadget id="calculator">21 * 14</gadget>
<output>294</output>

<gadget id="calculator">294 + 13</gadget>
<output>307</output>

<result>307</result>