第十七周OJ项目 A计算该日在本年中是第几天

#include <stdio.h>
struct y_m_d
{
int year;
int month;
int day;
};

int main()
{
struct y_m_d date;
int days(struct y_m_d date);
int day_sum;
scanf("%d%d%d",&date.year,&date.month,&date.day);
day_sum=days(date);
printf("%d\n",day_sum);
return 0;
}

int days(struct y_m_d date)
{
int sum;
sum=date.day；
int a[13]= {0,31,28,31,30,31,30,31,31,30,31,30,31};
int i;
for(i=1; i<date.month; i++)
{
sum+=a[i];
}
if(date.month>2&&((date.year%4==0&&date.year%100!=0)||date.year%400==0))
sum++;
return sum;
}