求大神帮我看看是哪里错了
#include <stdio.h>
int main()
{
int year = 2008;
int month = 8;
int day = 8;
int sum,flag;
switch(month)
{
case 1:sum=0;break;
case 2:sum=31;break;
case 3:sum=59;break;
case 4:sum=90;break;
case 5:sum=120;break;
case 6:sum=151;break;
case 7:sum=181;break;
case 8:sum=212;break;
case 9:sum=243;break;
case 10:sum=273;break;
case 11:sum=304;break;
case 12:sum=334;break;
default:printf("一年只有12个月");break;
}
sum=sum+day;
if(year%100==0&&year%4==0||year%4==0)
flag=1;
else
flag=0;
if(month>2&&flag==1)
sum++;
printf("%d年%d月%d日是该年的%d天\n",year,month,day,sum);
return 0;
}