The average of five numbers (some of which may be equal) is 2, and they are arranged in a row from largest to smallest, and the middle number is 2.2. What is the smallest difference between the first number and the fifth number?
五个数(有的可以相等)的平均数是2，按照从大到小排成一列，中间的数是2.2，则第一个数减第五个数的差最小是多少．
<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">2.2 * 3</gadget>
<output>6.6</output>

<gadget id="calculator">10 - 6.6</gadget>
<output>3.4</output>

<gadget id="calculator">3.4 / 2</gadget>
<output>1.7</output>

<gadget id="calculator">2.2 - 1.7</gadget>
<output>0.5</output>

<result>0.5</result>