There is a rectangular floor tile with a length of 42 centimeters and a width of 28 centimeters. Several pieces of this kind of square bricks can be used to pave a square floor. What is the minimum length of the side of the square ground?
有一种长方形地砖，长42厘米，宽28厘米，用这种方砖若干块刚好铺成一块正方形地面．正方形地面的边长最少是多少厘米？
<gadget id="calculator">2 * 7 * 3 * 2</gadget>
<output>84</output>

<result>84</result>