A cube glass tank without a cover, the side length is 4 decimeters, the water surface is 0.5 decimeters away from the fish tank mouth, how much water is in this fish tank.
一个无盖的正方体玻璃缸，棱长是4分米，水面距鱼缸口0.5分米，这个鱼缸装了多少水．
<gadget id="calculator">4 - 0.5</gadget>
<output>3.5</output>

<gadget id="calculator">4 * 4 * 3.5</gadget>
<output>56</output>

<result>56</result>