skyscraper has 100 floors above ground and 15 floors underground, and the underground is a parking lot. The payment method for the monthly elevator usage fee of this building is: the number of floors the elevator passes from the parking lot floor to the living floor multiplies 10 yuan. If a resident on the 15th floor of the building parks his car on the 15th floor underground of the parking lot, how much is his monthly elevator usage fee? (The skyscraper does not have 0 floors, the ground floor is above the ground floor)
一幢摩天大楼在地上有100层，在地下有15层，地下都是停车场．这个大楼每月电梯使用费的支付方式是：电梯从停车场楼层到居住楼层经过的楼层数乘以10元．若大楼第15层某住户将车停在停车场地下15层，那么每月他的电梯使用费是多少元．(该摩天大楼没有0层，地下一层上面是地上一层)
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">15 + 14</gadget>
<output>29</output>

<gadget id="calculator">10 * 29</gadget>
<output>290</output>

<result>290</result>