There is a four-digit number, add a decimal point after one of its digits, and add it to the original number to get 4003.64. What is the four-digit number?
有一个四位数，在它的某位数字后面加上一个小数点，再与原数相加得4003.64，这个四位数是多少？
<gadget id="calculator">100 + 1</gadget>
<output>101</output>

<gadget id="calculator">4_003.64 / 101</gadget>
<output>39.64</output>

<gadget id="calculator">39.64 * 100</gadget>
<output>3_964</output>

<result>3_964</result>