starting_x, starting_y, starting_z = gps.locate(5)

possible_sides = {"left", "right"}

function get_opposite_side()
    local side = read()
    if side == "left" then
        return possible_sides[2]
    elseif side == "right" then
        return possible_sides[1]
    else
        return get_side()
    end
end

function is_int(number)
    return (type(number) == "number") and (math.floor(number) == number)
end

function get_num()
    local blocks_to_dig = read()
    if not is_int(blocks_to_dig) then
        return get_num()
    else
        return tonumber(blocks_to_dig)
    end
end

blocks = get_num()

function turn_around(side)
    local func_table = {["left"] = turtle.turnLeft, ["right"] = turtle.turnRight}
    func_table[side]()
    turtle.dig()
    turtle.foward()
    func_table[side]()
    main_loop()
end

function dig_column()
    if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < 1 then
        turtle.refuel()
    end

    local success, data = turtle.inspectUp()

    local blocks_dug_up = 0

    while success and (data.name ~= "minecraft:air") do
        turtle.digUp()
        turtle.up()
        blocks_dug_up = blocks_dug_up + 1
        success, data = turtle.inspect()
    end

    if table.pack(turtle.inspect())[2].name ~= "minecraft:air" then
        turtle.dig()
    end

    turtle.forward()

    if blocks_dug_up ~= 0 then
        for i = 0, index - 1, 1 do
            turtle.digDown()
            turtle.down()
        end
    end
end

function main_loop()
    local blocks_dug_front = 0
    while blocks_dug_front ~= blocks do
        dig_column()
        blocks_dug_front = blocks_dug_front + 1
    end
    turn_side = get_opposite_side()
    turn_around(turn_side)
end