To celebrate Children's Day, the students of Class 4 and Class 1 are going to decorate the classroom. They hang a lantern every 1 meter on both sides of the classroom (not at both ends). The monitor measures the classroom to be 8 meters long. How many lanterns do they need to buy in total?
为庆祝六一儿童节，四1班的同学们准备把教室装扮一下．他们在教室的两边每隔1米挂一个灯笼(两端不挂)，班长量出教室长8米，他们一共需要买几个灯笼？
<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<result>14</result>