What is the sum of the 80th formula among the addition formulas 3+4, 5+9, 7+14, 9+19, 11+24... listed according to certain rules.
按照一定规律列出的加法算式3+4、5+9、7+14、9+19、11+24…中第80个算式的和是多少．
<gadget id="calculator">2 * 80</gadget>
<output>160</output>

<gadget id="calculator">160 + 1</gadget>
<output>161</output>

<gadget id="calculator">5 * 80</gadget>
<output>400</output>

<gadget id="calculator">400 - 1</gadget>
<output>399</output>

<gadget id="calculator">161 + 399</gadget>
<output>560</output>

<result>560</result>