"""
CSE 163
Suh Young Choi
Lesson 4: area_codes

Write a function area_codes that takes a list of str as
input where each str in the list is a phone number and
returns the number of unique area codes found in those phone
numbers. Each phone number will be of the format '123-456-7890'
and the area code is the first three characters in the str.

For example, if we were to call

area_codes([
    '123-456-7890',
    '206-123-4567',
    '123-000-0000',
    '425-999-9999'
])

This call would return 3 because there are 3 unique area-codes in these phone numbers (123, 206, 425).
"""

# Define your function up here!


def main():
    print(area_codes([
        '123-456-7890',
        '206-123-4567',
        '123-000-0000',
        '425-999-9999'
    ]))


if __name__ == '__main__':
    main()