说明：  用c语言编写的一些有趣题目的源代码，比如：一个商人骑一头驴要穿越1000公里长的沙漠，去卖3000根胡萝卜。已知驴一次性可驮1000根胡萝卜，但每走1公里又要吃掉1根胡萝卜。问：商人最多可卖出多少胡萝卜。共有3题
(Some interesting topics using the c language source code, for example: a businessman riding a donkey through the 1000 km long in the desert, to sell the 3000 carrots. Known donkey disposable pack 1000 carrots, but every one kilometer have to eat a carrot. Q: merchants sell carrots. Question 3 )