/*
 *??? 
 *2010 - 11 - 30 
 *?????5 - ???? 
 */
int main()
{
    int fun ( char [], int );//???? 
    char alp[501];
    cin >> alp;
    int i, j, k, l;
    l = strlen( alp );
    for ( i = 2; i <= l; i = i + 2 )//??????????????????????????????? 
    {
        for ( j = 0; j <= l - i; j++ )//???????????l-i? 
        {
            char str[501];
            for ( k = 0; k < i; k++ )
            {
                str[k] = alp[k + j];
            }
            str[i] = '\0';//?str???????????? 
            if ( fun ( str, i ) )//?????????????? 
               cout << str << endl;
        }
    }
    return 0;
}
int fun ( char str[], int a )
{
    int i, flag = 1;//flag???????????? 
    for ( i = 0; i <= a / 2; i++ )
    {
        if ( str[i] != str[a - i - 1] )//?????? 
        {
             flag = 0;//???? 
             return 0;//??0 
             break;
        }
    }
    if ( flag )//????? 
       return 1;//??1 
}
