C言語作成入力年月日、この日付の翌日の日付を出力

#include 
main()
{ int year,month,day,flag=0;
m:
  printf("Please input year month day:");
  scanf("%d%d%d",&year,&month,&day);
  if((year%4==0&&year%100!=0)||year%400==0)
	  flag=1;
  if(month==2)
  { if((day==28&&flag==0)||(day==29&&flag==1))
	{ day=1;
	  month++;
	}
    else if(day==29&&flag==0)
	{ printf("There is not 29th February!
",year);
	  goto m;
	}
		 else day++;
  }
  else if(month==12)
  { if(day==31)
  { day=1;
    month=1;
    year++;
  }
    else day++;
  }
       else	if(month==1||month==3||month==5||month==7||month==8||month==10)
	   { if(day==31)
	   { day=1;
         month++;
	   }
         else day++;
	   }
            else 
			{ if(day==30)
			{ day=1;
              month++;
			}
              else day++;
			}
  printf("the next day is %4d %4d %4d
",year,month,day);
}