def get_position(row_index, col_index, board_size):
    """(int, int, int) -> int

    Return the str_index of the cell in the game board of size board_size within the row, row_index, and the column, col_index

    >>>get_position(1, 1, 2)
    0
    >>>get_position(3, 2, 3)
    7
    """

    return (row_index - 1) * board_size + col_index - 1