Divide 135 apples into several parts and the number of apples in any two parts is different. What is the maximum number of parts that can be divided.
把135个苹果分成若干份且任意两份的苹果数都不相同，最多可以分多少份．
<gadget id="calculator">135 - 120</gadget>
<output>15</output>

<result>15</result>