def is_Double(string):
    lef_str = len(string)
    if string[:lef_str // 2] == string[-lef_str // 2:]:
        return True
    return False


def main():
    s = input()
    if is_Double(s):
        print('YES')
    else:
        print('NO')
    return


if __name__ == '__main__':
    main()