It's easy to create duplicates without realizing it. (I've modified the Sleak tool to find duplicates and am contributing this and other useful Sleak changes back to Eclipse.)
很容易创建副本，而且您可以都没有意识到(我曾修改了Sleak工具使之发现副本，并将此改变以及其他有用的改变添加到Eclipse中。)
Exactly. Mathematicians write 365 30. And what is the number of possible sets of 30 birthdays without any duplicates?
很好，数学家会将其写做365 30。那么30个不重复的生日组合会是多少？
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