运行后出来的是8天，小白不知道错在哪里。

#include <stdio.h>
int main() 
{ 
    int year = 2008;
    int month = 8;
    int day = 8;
    int sum;
    switch(month)
    {
        case1:sum=0;break;
        case3:
        if(year%400==0||(year%4==0&&year%400!=0))
        {
            sum+=29;
        }
        else
        {
            sum+=28;
        }
        break;
        case2:sum+=31;
        case4:sum+=30;
        case5:sum+=31;
        case6:sum+=30
        case7:sum+=31;
        case8:sum+=31;
        case9:sum+=30;
        case10:sum+=31;
        case11:sum+=30;
        case12:sum+=31;break;
    }
    sum=sum+day;
    printf("%d年%d月%d日是该年的第%d天",year,month,day,sum);
 return 0;
 }