def get_grade_suffix(grade):
    """
    Select correct ordinal suffix
    """
    ordinal_map = {(1): 'st', (2): 'nd', (3): 'rd'}
    teens_map = {(11): 'th', (12): 'th', (13): 'th'}
    return teens_map.get(grade % 100, ordinal_map.get(grade % 10, 'th'))
