编写一个函数。当给出月份号，程序返回一年中到该月为止（包括该月）总共的天数。假定在外部声明了以下的结构模板和一个该结构的数组。
#include <stdio.h>
struct house {
float sqft;
int rooms;
int stories;
char address[40];
};
int main (void)
{
struct house fruzt = {1560.0, 6, 1, "22 Spiffo Road"};
struct house *sign;
sign = &fruzt;
printf ("%d %d\n", fruzt.rooms, sign->stories);
printf ("%s \n", fruzt.address);
printf ("%c %c\n", sign->address[3], fruzt.address[4]);
return 0;
} 
extern struct month months[ ]; int days (int month) { int index, total; if (month < 1 l l month > 12) return (-1); /* 错误标志 */ else { for (index = 0, total = 0; index < month; index ++) total += months[index] .days; return (total); } }