Cut a cube of plasticine into 64 small cubes of the same size with a knife. No movement or overlapping is allowed. At least how many knives should be cut.
把一块正方体的橡皮泥块，用刀切成64块大小一样的小正方体，不许移动、重叠，至少要切多少刀．
<gadget id="calculator">3 + 3 + 3</gadget>
<output>9</output>

<result>9</result>