On both sides of a street, there is a street lamp at an average interval of 42 meters, and there are 24 street lamps from the beginning to the end. How long is this street?
一条街道的两侧平均每隔42米装有一盏路灯，从头到尾共有24盏，这条街道有多长？
<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<gadget id="calculator">11 * 42</gadget>
<output>462</output>

<result>462</result>