例题：输入某年某月某日，判断这一天是这一年的第几天？

程序如下：

#include "stdio.h"
#include "conio.h"

void main()
{
int day,year,month,sum,leap; （这行要是这样写结果就出错：int year,month,day,sum,leap;）
printf("\nplease input year,month,day\n");
scanf("%d,%d,%d",&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("data error");break;
}
sum=sum+day;
if(year%400==0||(year%4==0&&year%100!=0))
leap=1;
else
leap=0;
if(leap==1&&month>2)
sum++;
printf("It is the %dth day.",sum);
getch();
}
有哪位高手能指点一二？