判断某月某天是这年的第几天

#include<stdio.h>
int getyearday(int year,int month,int day);
int isleap(int year);
int main()
{
   int year,month,day;
   scanf("%d%d%d",&year,&month,&day);
   printf("%d",getyearday(year,month,day));
   return 0;
}
int getyearday(int year,int month,int day)
{
    int k,leap;
    int tab[2][13]={{0,31,29,31,30,31,30,31,31,30,31,30,31},{0,31,28,31,30,31,30,31,31,30,31,30,31}};
    leap=isleap(year);
    for(k=1;k<month;k++)
            day=day+tab[leap][k];
    return day;
}
int isleap(int year)
{
    return((year % 4 == 0&& year % 100 !=0)|| year % 400 == 0);
}