A regular pentagonal swimming pool needs to be installed with guardrails, 15 on each side, and installed on each corner. How many guardrails are needed in total?
一个正五边形的游泳池的周围要安装护栏，每边安15根，每个角上都要安装，一共需要多少根？
<gadget id="calculator">15 * 5</gadget>
<output>75</output>

<gadget id="calculator">75 - 5</gadget>
<output>70</output>

<result>70</result>