Uses crt;
var st: string;
function KT (xau: string): boolean;
var i, dem: integer;
begin
dem:=0;
for i:= 1 to length(st) div 2 do
if xau<>xau[length(xau)-i+1] then
inc(dem);
if dem<>0 then
KT:=False
else
KT:=True;
end;
begin
clrscr;
write ('Nhap so co do dai khong qua 100 chu so: ');
readln (st);
if length(st)>100 then
begin
write ('Nhap khong hop le! An Enter va chay lai!');
readln;
exit;
end;
if KT(st)=True then
write ('Day la so doi xung!')
else
write ('Day la so khong doi xung!');
readln;
end.
