uses crt;
var S : string;
    i, j, k : byte;
    
begin
    clrscr;
    write('Nhap xau = '); readln(S);
    
    k := 0; i := 1; j := length(S);
    while (i <= j) and (k = 0) do
        begin
            if S[i] <> S[j] then k := 1;
            i := i + 1;
            j := j - 1;
        end;
    
    if k = 1 then write('Xau khong doi xung')
    else write('Xau doi xung');
    
    readln
end.

#include <iostream>
#include <string>
#include <algorithm>
#define str string
#define rvs [](str s){reverse(s.begin(), s.end()); return s;}
using namespace std;
int main()
{
    str s;
    cin >> s;
    cout << (s==rvs(s)?"doi xung":"khong doi xung");
}

$\\$

`@Daoanhviet96`