Câu 1:
uses crt;
var a,b:longint;
begin
clrscr;
repeat
write('Nhap chieu dai,rong (a>0,b>0,a>b): '); read(a,b);
if (a<=0) or (b<=0) or (b>=a) then writeln('NHAP LAI!');
until (a>0) and (b>0) and (a>b);
writeln('Dien tich HCN: ',a*b);
writeln('Chu vi HCN: ',2*(a+b));
readln
end.
Câu 2:
uses crt;
var n,t:longint;s:string;
begin
clrscr;
repeat
write('Nhap n co 3 chu so: '); readln(s);
if length(s)<>3 then writeln('NHAP LAI!');
until length(s)=3;
val(s,n);
while n<>0 do
begin
t:=t+(n mod 10);
n:=n div 10;
end;
writeln('Tong: ',t);
readln
end.