""" day_01_02.py """

# usage: python3 day_01_02.py


def get(filename):
    """ contents of filename """
    with open(filename, 'r', encoding='utf-8') as infile:
        data = infile.read().strip()

    return data


def test(data, solution):
    """ testing """
    assert len(data) % 2 == 0
    output = solve(data)
    assert output == solution


def solve(data):
    """ solve the puzzle """
    size = len(data)
    j = size // 2
    output = [int(d) for i, d in enumerate(data) if d == data[(i + j) % size]]

    return sum(output)


if __name__ == '__main__':
    test(get('example05'), 6)
    test(get('example06'), 0)
    test(get('example07'), 4)
    test(get('example08'), 12)
    test(get('example09'), 4)

    puzzle = get('input')
    x = solve(puzzle)

    print(x)