gravel_dig

local length = tonumber(arg[1])

local function CheckInventorySpace()
    while true do
        for i=1,16 do
            if turtle.getItemCount(i) == 0 then
                return
            end
        end

        input("Inventory full, please clear inventory then press enter to continue...")
    end
end

turtle.digDown()
turtle.digUp()
for i=1,length do
    local sucked = false
    repeat
        CheckInventorySpace()
        local dug = turtle.dig()

        CheckInventorySpace()
        sucked = turtle.suckUp()
        if sucked and not dug then
            sleep(0.1)
        end
    until (not sucked) and turtle.forward()

    CheckInventorySpace()
    turtle.digUp()

    CheckInventorySpace()

    local success, info = turtle.inspectDown()
    if success and (info.name == "minecraft:sand" or info.name == "minecraft:gravel") then
        CheckInventorySpace()
        turtle.digDown()
    end
end