There is a three-digit number, write the number 6 in front of it, you can get a four-digit number, if you write 6 behind it, you can also get a four-digit number, and the sum of these two four-digit numbers is 9999, what is the original three-digit number?
有一个三位数，将数码6写在它的前面，则可得到一个四位数，如果把6写在它的后面，也可得到一个四位数，且这两个四位数的和是9999，原来的三位数是多少．
<gadget id="calculator">6 * 1_000</gadget>
<output>6_000</output>

<gadget id="calculator">9_999 - 6_000 - 6</gadget>
<output>3_993</output>

<gadget id="calculator">1 + 10</gadget>
<output>11</output>

<gadget id="calculator">3_993 / 11</gadget>
<output>363</output>

<result>363</result>