There are 3 boxes, and every two boxes are weighed together, and their weights are 63 kg, 65 kg, and 66 kg respectively. How much is the heaviest box heavier than the lightest box?
有3个箱子，每两箱合称一次，称得它们的重量分别是63千克，65千克和66千克，最重的箱子比最轻的箱子重多少千克．
<gadget id="calculator">63 + 65 + 66</gadget>
<output>194</output>

<gadget id="calculator">194 / 2</gadget>
<output>97</output>

<gadget id="calculator">97 - 63</gadget>
<output>34</output>

<gadget id="calculator">97 - 66</gadget>
<output>31</output>

<gadget id="calculator">34 - 31</gadget>
<output>3</output>

<result>3</result>