Cut off a handkerchief with a side length of 18 cm from a piece of square fabric, or sew a towel with a side length of 27 cm. There is no excess fabric. What should be the minimum side length of this square piece of fabric?
一块正方形布料剪去边长是18厘米的手帕，或缝边长是27厘米的毛巾，布料没多余，这块正方形布料的边长最少应该是多少．
<gadget id="calculator">3 * 3 * 2 * 3</gadget>
<output>54</output>

<result>54</result>