There are three piles of exercise books, pile A has 120 books, pile B has 150 books, and pile C has 180 books. Now divide them into small piles with the same number of books, and no surplus is allowed. How many piles can they be divided into at least?
有三堆练习本，甲堆有120本，乙堆有150本，丙堆有180本，现在将它们都分成同样本数的小堆，而不准有剩余，最少可以分成几堆？
<gadget id="calculator">120 + 150 + 180</gadget>
<output>450</output>

<gadget id="calculator">2 * 3 * 5</gadget>
<output>30</output>

<gadget id="calculator">450 / 30</gadget>
<output>15</output>

<result>15</result>