Fold a piece of rectangular paper with a length of 18 cm and a width of 12 cm into square cells of the same size. There should be no leftovers. What is the maximum size of each cell?
把一张长18厘米，宽12厘米的长方形纸，折成大小相同的正方形小格，不能有剩余，每小格最大是多少厘米？
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>