uses crt;

var a,b,c: integer;

begin

clrscr;

write('Nhap ngay; thang; nam :'); readln(a,b,c);

if (a>=1) and (a<=31) then write('Ngay hop le');

if (b>=1) and (b<=12) then write('Thang hop le');

if (c>=0) and (c<=2021) then write('Nam hop le');

readln

end.

uses crt;

var day,month,year: byte;

begin

clrscr;

write ('nhap ngay: ');  readln (day);

write ('nhap thang: ');  readln (month);

write ('nhap nam: ');   readln (year);

if year mod 4=0 then 

if month=2 then

if day<>29 then writeln ('ngay khong hop le')

else writeln ('ngay hop le');

if (month=1) or (month=3) or (month=5) or (month=7) or (month=8) or (month=10) or (month=12) then 

if day<>31 then writeln ('ngay khong hop le') else writeln ('ngay hop le');

if (month=4) or (month=6) or (month=9) or (month=11) then 

if day<>30 then writeln ('ngay khong hop le') else writeln ('ngay hop le');

if (month<=0) or (month>12) then writeln ('Thang khong hop le') 

else writeln ('Thang hop le');

if (year<0) then writeln ('Nam khong hop le')

else writeln ('nam hop le');

readln;

end.