A number is divided by 4, the quotient is 81, and the remainder is 1. What is this number?
一个数除以4，商81，余数是1，这个数是多少．
<gadget id="calculator">4 * 81</gadget>
<output>324</output>

<gadget id="calculator">324 + 1</gadget>
<output>325</output>

<result>325</result>