Pearl Air Conditioning shipped in a batch of air conditioners, and sold 15 air conditioners on the first day, and twice as much on the second day, and if they sold 28 air conditioners on the third day, there would be no stock to sell in the store. How many units did the air conditioner store purchase in total?
明珠空调运进一批空调，第一天卖出15台空调，第二卖出的是第一天的2倍，第三天如果卖出28台空调，那么店中将无货可卖，这次空调店共进货多少台？
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">15 + 30 + 28</gadget>
<output>73</output>

<result>73</result>