digits are composed of numbers 0, 2, 4, and 7. Each digit is required to be used and repeated use is allowed, so how many different six digits can be formed.
由数字0，2，4，7组成6位数，要求每个数字都要用到，允许重复使用，那么能组成多少个不同的六位数．
<gadget id="calculator">3 * 5 * 4 * 3 * 2 * 1</gadget>
<output>360</output>

<gadget id="calculator">1 * 4 * 3 * 2 * 1</gadget>
<output>24</output>

<gadget id="calculator">3 * 1 * 3 * 2 * 1</gadget>
<output>18</output>

<gadget id="calculator">3 * 2 * 1 * 2 * 1</gadget>
<output>12</output>

<gadget id="calculator">24 + 18 + 12 + 6</gadget>
<output>60</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">60 + 20</gadget>
<output>80</output>

<gadget id="calculator">80 * 3</gadget>
<output>240</output>

<gadget id="calculator">60 + 30 + 30</gadget>
<output>120</output>

<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<gadget id="calculator">120 + 30</gadget>
<output>150</output>

<gadget id="calculator">150 * 2</gadget>
<output>300</output>

<gadget id="calculator">360 + 240 + 120 + 240 + 150 + 300</gadget>
<output>1_410</output>

<result>1_410</result>