import re


def title_case(s):
    """Convert a string to title case, with some grammatical exceptions.

    Args:
        s (str, utf-8): original string to be Title Cased.
    Returns:
        A Title Cased string.
    """
    articles = ['a', 'an', 'of', 'the', 'is']
    word_list = re.split(' ', s)
    final = [word_list[0].capitalize()]
    for word in word_list[1:]:
        final.append(word if word in articles else word.capitalize())
    return " ".join(final)