如果你带着一张废纸，假如你已经按如下方式启动了您的程序。

If you have a piece of scrap paper with you, suppose that you've started your program as follows.

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如果我已经告诉过您一次，那么我就已经告诉您两次了。

If I've told you once, I've told you twice.

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如果这些文件已经存在，在您继续这个练习之前请进行备份。

If these files already exist, make backups before you continue with this exercise.

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