Divide 135 people into several groups. If any two groups have different numbers of people, how many groups can they be divided into?
将135人分成若干个小组，要任意两个组的人数都不相同，至多可以分成多少个组？
<gadget id="calculator">135 - 120</gadget>
<output>15</output>

<result>15</result>