Among the 1000 natural numbers 1001, 1002, ... 2000, how many pairs of adjacent natural numbers can be found so that they do not carry when added.
在1001，1002，…2000这1000个自然数中，可以找到多少对相邻的自然数，使它们相加时不进位．
<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">5 * 5 * 5</gadget>
<output>125</output>

<gadget id="calculator">125 - 1</gadget>
<output>124</output>

<gadget id="calculator">1 + 5 + 25 + 124</gadget>
<output>155</output>

<result>155</result>