80分，求大神帮忙

#include<cstdio>
#include<algorithm>
int day(int n)
{
    int year=n/10000,mon=n%10000/100,day=n%100;
    if(mon>12||day>30||mon==0||day==0)return 1;
    if(mon==1||mon==3||mon==5||mon==7||mon==8||mon==10||mon==12)
    if(day<=31)
    return 0;
    if(mon==4||mon==6||mon==9||mon==11)
    if(day<=30)
    return 0;
    if(mon==2)
    {
        if(year%4==0&&year%100!=0)
        if(day<=29)
        return 0;
        else if(year%400==0)
        if(day<=29)
        return 0;
        else{
            if(day<=28)
            return 0;
        }
    }
    return 1;
}
int main()
{
     int a1,a2,year1,year2,j,count=0;
     scanf("%d%d",&a1,&a2);
     year1=a1/10000;
     year2=a2/10000;
     for(int i=year1;i<=year2;i++)
     {
         j=i*10000+i%10*1000+i%100/10*100+i%1000/100*10+i/1000;
         if(day(j)==0&&j>=a1&&j<=a2)
         count++;
     }
     printf("%d\n",count);
     return 0;
}