class Board(object):
    def __init__(self, wide, tall):
        self.__wide__ = wide
        self.__tall__ = tall
        self.__area__ = [[None for _ in range(wide)] for _ in range(tall)]

        self.__validate_wide__(wide)
        self.__validate_tall__(tall)

    def __validate_wide__(self, wide):
        if wide <= 0:
            raise Exception('Wide must be greater than zero')

    def __validate_tall__(self, tall):
        if tall <= 0:
            raise Exception('Tall must be greather than zero')

    def __validate_ranges__(self, left, top, right, bottom):
        if left < 0:
            raise Exception('Left must be greater than zero')

        if right >= self.__wide__:
            raise Exception('Right must be less than {0}'.format(self.__wide__))

        if top < 0:
            raise Exception('Top must be greater than zero')

        if bottom >= self.__tall__:
            raise Exception('Bottom must be less than {0}'.format(self.__tall__))

        if left > right:
            raise Exception('Left must be less than right')

        if top > bottom:
            raise Exception('Bottom must be less than top')

    def __validate_position__(self, index_j, index_i):
        if index_j < 0:
            raise Exception('X must be greater than zero')

        if index_j >= self.__wide__:
            raise Exception('X must be less than {0}'.format(self.__wide__))

        if index_i < 0:
            raise Exception('Y must be greater than zero')

        if index_i >= self.__tall__:
            raise Exception('Y must be less than {0}'.format(self.__tall__))

    def area(self):
        return self.__area__

    def fill_area(self, char, left, top, right, bottom):
        self.__validate_ranges__(left, top, right, bottom)
        # index_j controls left and right
        # index_i controls top and bottom
        for index_i in range(top, bottom + 1):
            for index_j in range(left, right + 1):
                self.__area__[index_i][index_j] = char

    def fill_position(self, char, index_j, index_i):
        self.__validate_position__(index_j, index_i)
        self.__area__[index_i][index_j] = char

    def clear_position(self, index_j, index_i):
        self.__validate_position__(index_j, index_i)
        self.__area__[index_i][index_j] = None