Huimin Supermarket conducts promotional activities, and the regulations are as follows: If the price of a single purchase does not exceed 500 yuan, a 10% discount will be given; if the price of a single purchase exceeds 500 yuan, a 10% discount will be given for the part of 500 yuan, and a 20% discount will be given for the part exceeding 500 yuan discount. Aunt Li went to the supermarket twice to shop and paid 270 yuan and 450 yuan respectively. If Aunt Li makes a one-time purchase, how much does she only need to pay?
惠民超市进行促销活动，规定如下：如果一次购物按标价不超过500元，给予九折优惠；如果一次购物标价超过500元，其中500元部分给予九折优惠，超过500元的部分给予八折优惠．李阿姨先后两次去该超市购物，分别付款270元和450元．如果李阿姨一次性购买，只要付款多少元？
<gadget id="calculator">500 * 0.9</gadget>
<output>450</output>

<gadget id="calculator">450 - 500</gadget>
<output>-50</output>

<gadget id="calculator">270 + (-50)</gadget>
<output>220</output>

<gadget id="calculator">220 * 0.8</gadget>
<output>176</output>

<gadget id="calculator">450 + 176</gadget>
<output>626</output>

<result>626</result>