定义一个结构体变量（包括年、月、日），计算该日在本年中为第几天？

（注意考虑闰年问题），要求写一个函数days，实现上面的计算。

由主函数将年月日传递给days函数，计算后将日子传递回主函数输出-Define a structure variable (year, month, day), calculate the day for the first few days of the year? Attention to consider the leap year problem, and asked to write a function days to achieve the above calculations. To days date passed to the function, calculated after day passed back by the main function of the main function output