这样打代码哪里有错...求大神解答

#include <stdio.h>

int main() 

{ 

    int year = 2008;

    int month = 8;

    int day = 8;

    int i,sum;

    int Jan = 31;

    int Feb = 28;

    int Mar = 31;

    int Apr = 30;

    int May = 31;

    int Jun = 30;

    int Jul = 31;

    int Aug = 31;

    int Sep = 30;

    int Oct = 31;

    int Nov = 30;

    int Dec = 31;

    if(year%100==0&&year%400==0||year%4==0&&year%100!=0)i=1;

    else i=0;

    switch(month)

    {

        case 1:sum = Jan break;

        case 2:sum = Jan+Feb break;

        case 3:sum = Jan+Feb+Mar break;

        case 4:sum = Jan+Feb+Mar+Apr break;

        case 5:sum = Jan+Feb+Mar+Apr+May break;

        case 6:sum = Jan+Feb+Mar+Apr+May+Jun break;

        case 7:sum = Jan+Feb+Mar+Apr+May+Jun+Jul break;

        case 8:sum = Jan+Feb+Mar+Apr+May+Jun+Jul+Aug break;

        case 9:sum = Jan+Feb+Mar+Apr+May+Jun+Jul+Aug+Sep break;

        case 10:sum = Jan+Feb+Mar+Apr+May+Jun+Jul+Aug+Sep+Oct break;

        case 11:sum = Jan+Feb+Mar+Apr+May+Jun+Jul+Aug+Sep+Oct+Nov break;

        case 12:sum = Jan+Feb+Mar+Apr+May+Jun+Jul+Aug+Sep+Oct+Nov+Dec break;

    }

    if(i==1)sum+=1;

    printf("%d年%d月%d日是该年的第%d天",year,month,day,sum);

    return 0;

}