F you don't know what this one means, the number does not apply to you. If you are not 31337 and want to know how to become 31337, Wikipedia has a good article on it here.

如果你不知道31337是什么，那么这个数字对你就不适用了。

youdao

F: Really? How do you know which bills are marked?

朋友：真的吗？你们怎么知道哪些钱作了记号呢？

youdao

F: Girls are enlisted, and it is not only to fight these battles, you know, which is horrible.

F：女孩同样会被招募，而且不仅将她们投入到战场上，还有更为可怕的。

youdao

So input is an int called F, print out to the screen or your piece of paper the value of C. Odds are you only need two, maybe three lines of code for this, but the goal ultimately will be try it on your own.

所以输入是一个int类型的F，在你的屏幕上,或你们的纸上打印出C的数值,可能你们需要两行或者三行的代码,但是最终的目标需要你自己独自尝试。

哈佛公开课 - 计算机科学课程节选

As an aside, why are you able to use print F without writing out a prototype for it?

此外，为什么我们不用写printf的函数原型,而可以使用它呢？

哈佛公开课 - 计算机科学课程节选

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