gre数学题
the20peopleatapartyaredividedintonmutuallyexclusivegroupsinsuchawaythatthenumberofpeopleinanygroupdoesnotexceedthenumberofinanyothergroupbymorethan1
thenumberofn(ifatleastoneofthegroupsconsistsof3people)和6比
n大还是6大还是没法比
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