program phuongt;
uses crt;
var a: real;
begin
clrscr;
write('Nhap a = '); readln(a);
if a<0 then write(a, ' khong phai canh hinh vuong') else
begin
writeln('Chu vi hinh vuong canh a: ', a*4);
write('Dien tich hinh vuong canh a: ', a*a);
end;
readln
end.