def common_bit(lines: list, column_number: int) -> int:
    """common_bit take a list of strings representing binary numbers and a column number and return an int that can be 0, > 0 or < 0 if the number of 1s and 0s in that column are equal, more 1s or more 0s"""
    cb = 0
    for bits in lines:
        if bits[column_number] == 0:
            cb -= 1
        elif bits[column_number] == 1:
            cb += 1
    return cb