这个怎么编，求解答啊

#include <stdio.h>
int main()
{
    int year,month,day,sum,add;
    scanf("%d年%d月%d日",&year,&month,&day); 
    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("输入错误");break;
    }
    sum=sum+day;
    if(year%400==0||(year%4==0&&year%100!=0))
     {
        add=1;
    } else {
       add=0;
    }
    if(add==1&&month>2) {
        sum=sum+1;
    }
    printf("这是这一年的第 %d 天。",sum);
    return 0;
}