求助！！用pascal设计电子月历的程序。

const w:array[1..12]of byte=(1,4,4,0,2,5,0,3,6,1,4,6);
var year:word;month,week,days:byte;
begin
repeat
write('Input year(1901~2099):');
readln(year)
until (year>1900)and(year<2100);
repeat write('Input month(1~12):');readln(month)until month in [1..12];
writeln(' ====',year,'.',month,'====');
dec(year,1900);
week:=(w[month]+year+year div 4-byte((year mod 4=0)and(month<=2)))mod 7;
writeln(' SUN MON TUE WED THU FRI SAT');
write('':week*4);
for days:=1 to 31-byte(month in[4,6,9,11])-byte(month=2)*3+byte((month=2)and(year mod 4=0))do
if (days+week) mod 7=0 then writeln(days:4)else write(days:4);
readln;
end.