这个为什么运行不了？

#include<stdio.h>
int main(int argc,char*argv[])
{
int year,month,day;
scanf("%dyear,%dmonth",&year,&month);
if ((year%400==0)||(year%4==0&&year%100!=0))
{
if (month==2)
day=29;
else if (month==1,month==3,month==5,month==7,month==8,month==10,month==12);
day=31;
else if(month==4,month==6,month==9,month==11);
day=30;
}
else

{
     if (month==2)
     day=28;
    else if (month==1,month==3,month==5,month==7,month==8,month==10,month==12);
     day=31;
    else if(month==4,month==6,month==9,month==11);
    day=30;
    
}
 printf("%d",day);

}