def test():
    test_data = [
        ("12321", True),
        ("1221", True),
        ("123", False),
        ("111", True),
        ("1122", False),
        ("111", True),
        ("1", True),
        ("ada", True),
        ("aaa", True),
        ("bacb", False)
    ]
    fl = 0
    for a, res in test_data:
        try:
            if (is_palindrome(a) == res):
                fl = 1
            else:
                raise Exception
        except Exception:
            print("NO")
            fl = 0
            break
    if (fl == 1):
        print("YES")