There are several balls in a school, if they are distributed to 10 classes on average, there are 9 balls left, if they are distributed to 12 classes on average, 11 balls are left, if they are distributed to 15 classes on average, 14 balls are left, how many balls does the school have at least?
某校有皮球若干个，如平均分给10个班则余下9个，如平均分给12个班则余下11个，如平均分给15个班则余下14个，学校至少有多少个皮球．
<gadget id="calculator">2 * 5 * 3 * 2</gadget>
<output>60</output>

<gadget id="calculator">60 - 1</gadget>
<output>59</output>

<result>59</result>