program kiemtra;
uses crt;
var st:string;
i:byte;
kt:boolean;
begin
clrscr;
write('Nhap xau: '); readln(st);
kt:=true;
for i:=1 to length(st) div 2 do
if st[i]<>st[length(st)-i+1] then kt:=false;
if kt=true then write('Doi xung')
else write('Khong doi xung');
readln
end.