Keep Getting an Unknown Error on code challenge!

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.

def num_teachers(dictionary):
    count = 0
    for teachers in dictionary:
        count += 1
    return count

def num_courses(dictionary):
    count = 0
    for courses in dictionary.values():
        count += len(courses)
    return count

def courses(dic):
    list = []
    for courses in dic.values():
        for stuff in courses:
            list.append(stuff)
    return list

def most_courses(dic):
    max_num_courses = 0
    for key, value in dic.items():
        if len(v) > m_courses:
            m_courses = len(v)
            teacher = k
    return teacher