编写一个输入某年月日,判断这一天是这一年的第几天的程序

#include<stdio.h>
int main()
{
int year,month,day,sum,leap;
printf("Please enter year,month,day (just like:2009,9,9)\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("Enter wrong!Please enter right date.\n");
break;
}
sum=sum+day;
if (year%4==0&&year%100!=0||year%400==0)
leap=1;
else
leap=0;
if(leap==1&&month>2)
sum=sum+1;
printf("It is the %dth day.",sum);
return 0;
}