There are several stacks of 2-yuan and 5-yuan banknotes. Divide them into two piles with the same amount of money. The first pile has the same number of 2-yuan and 5-yuan notes, and the second pile has the same number of 2-yuan and 5-yuan bills. So how much is this stack of money at least?
现有一叠2元和5元的纸币若干，把它们分成钱数相同的两堆，第一堆中2元和5元的张数相同，第二堆中2元和5元的钱数相等，那么这一叠钱至少有多少元．
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">7 * 20</gadget>
<output>140</output>

<gadget id="calculator">2 * 140</gadget>
<output>280</output>

<result>280</result>