Ding Ding plans to finish reading a book of "Grimm's Fairy Tales" in 18 days, but Kaka takes 3 days longer than Ding Ding to read it. It is known that Ding Ding reads 4 more pages than Kaka every day. So, how many pages does this "Grimm's Fairy Tales" have?
丁丁计划18天看完一本《格林童话》，而卡卡比丁丁要多用3天看完，已知丁丁每天比卡卡多看4页．那么，这本《格林童话》共有多少页．
<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">18 * (4/3)</gadget>
<output>24</output>

<gadget id="calculator">18 + 3</gadget>
<output>21</output>

<gadget id="calculator">24 * 21</gadget>
<output>504</output>

<result>504</result>