Add a decimal point before a certain digit of a four-digit number, and add the result to the original number to get 2017.98. What is the four-digit number?
在一个四位数的某位数字前加上一个小数点，将所得的结果与原数相加得2017.98，此四位数是多少．
<gadget id="calculator">1 / 100</gadget>
<output>1/100 = around 0.01</output>

<gadget id="calculator">1 + (1/100)</gadget>
<output>101/100 = around 1.01</output>

<gadget id="calculator">2_017.98 / (101/100)</gadget>
<output>1_998</output>

<result>1_998</result>