When a number is divided by 26, the quotient and remainder are both 15. What is the number?
一个数除以26，商和余数都是15，这个数是多少．
<gadget id="calculator">26 * 15</gadget>
<output>390</output>

<gadget id="calculator">390 + 15</gadget>
<output>405</output>

<result>405</result>