uses crt;
var kt : boolean; s : string; i, j : byte;
begin
clrscr;
write('Nhap xau s : '); readln(s);
kt := true; i := 1; j := length(s);
while i <= j do begin
if s[i] <> s[j] then
begin kt := false; break end;
i := i + 1; j := j - 1; end;
if kt = true then write('Doi xung')
else write('Khong doi xung');
readln
end.