After Xiao Ming went to the stationery store to buy a pen, he found that the money he used was 0.5 yuan more than half of the total money he brought; then he bought a ballpoint pen, and the money he used was 0.5 yuan less than half of the money left after buying the pen ; I bought another 2.8 yuan notebook, and finally left 0.8 yuan. How much money did Xiao Ming bring?
小明去文具店买了1支钢笔后，发现所用的钱比所带的总钱数的一半多0.5元；接着买了1支圆珠笔，所用的钱比买钢笔后余下的钱的一半少0.5元；又买了2.8元的本子，最后剩下0.8元．小明带了多少元钱？
<gadget id="calculator">2.8 + 0.8</gadget>
<output>3.6</output>

<gadget id="calculator">3.6 - 0.5</gadget>
<output>3.1</output>

<gadget id="calculator">3.1 * 2</gadget>
<output>6.2</output>

<gadget id="calculator">6.2 + 0.5</gadget>
<output>6.7</output>

<gadget id="calculator">6.7 * 2</gadget>
<output>13.4</output>

<result>13.4</result>