There are three iron pipes, the lengths of which are 18cm, 12cm, and 42cm respectively. They should be cut into small iron pipes of the same length, and there should be no surplus. What is the longest centimeter of each iron pipe?
有三根铁管，长分别是18cm、12cm、42cm，要把它们截成同样长的小铁管，不能有剩余，每根铁管最长是多少厘米？
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<result>6</result>