哪里错了啊 看不出来啊

#include <stdio.h>
int main()
{
    /* 定义需要计算的日期 */
    int year = 2008;
    int month = 8;
    int day = 8;
    int sum =0,flag=0;
    /*
     * 请使用switch语句，if...else语句完成本题
     * 如有想看小编思路的，可以点击左侧任务中的“不会了怎么办”
     * 小编还是希望大家独立完成哦~
     */
    switch(month)
    {
        case 1:
            sum=0;
        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%400==0||(year%4==0&&year%100!=0))
        flag=1;
    else
        flag=0;
    if(flag==1&&month>2)
        sum++;
    printf("%d年%d月%d日是该年的第%d天"，year,month,day,sum);
    return 0;
}