A rectangular wooden board is 28dm long and 12dm wide. Under the premise that there is no surplus, cut it into a square of equal size and as large as possible. What is the side length of the square?
一张长方形木板长28dm，宽12dm，在无剩余的前提下，将它裁成大小相等且尽可能大的正方形，正方形的边长是多少？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>