What is the sum of all the simplest proper fractions whose fraction unit is (1/8).
分数单位是(1/8)的所有最简真分数的和是多少．
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">7 / 8</gadget>
<output>7/8 = around 0.875</output>

<gadget id="calculator">(1/8) + (3/8) + (5/8) + (7/8)</gadget>
<output>2</output>

<result>2</result>