In order to improve the living environment of residents, Jiangjun County has rebuilt both sides of the river. Originally, from the second bridge to the fifth bridge, a street lamp was installed every 45 meters, plus two at both ends, a total of 53 street lamps. Now instead of installing a street lamp every 60 meters, how many lamps do not need to be moved in the middle except for the two ends?
将军县为了改善居民生活环境，对河水两岸进行改造，原来从二桥到五桥之间，每隔45米安装一盏路灯，加上两端的两盏一共53盏路灯．现在改为每隔60米安装一盏路灯，除两端以外，中途有多少盏不必移动？
<gadget id="calculator">53 - 1</gadget>
<output>52</output>

<gadget id="calculator">45 * 52</gadget>
<output>2_340</output>

<gadget id="calculator">2_340 / 180</gadget>
<output>13</output>

<gadget id="calculator">13 - 1</gadget>
<output>12</output>

<result>12</result>