我是超级新手，只上了两堂课，碰到了个小问题，大哥大姐们帮帮我把。谢谢谢谢谢谢谢谢谢谢。。。题目是：输入年、月，判断该年该月份的天数。下面是我的答案，有些问题，希望能帮我找出来。再次感谢
program ~~~;
var year,month,days:integer;
begin
 readln(year,month);
 if(year mod 400=0) or (year mod 4=0)and(year mod 100<>0) then readln(month)
                                                                 case month of
                                                                 1,3,5,7,8,10,12:days:=31;
                                                                 4,6,9,11:days:=30;
                                                                 2:days:=28
                                                          else readln(month)
                                                                 case month of
                                                                 1,3,5,7,8,10,12:days:=31;
                                                                 4,6,9,11:days:=30;
                                                                 2:days:=29;
  writeln(days);
end.