function refuel()
    if turtle.getFuelLevel() < 10 then
    turtle.select(16)
    turtle.refuel(1)
    end
end

function moveForward()
    turtle.dig()
    turtle.forward()
end

function breakblocks()
    local success, data = turtle.inspectDown()
    if (success and data.name~="minecraft:grass" and  data.name~="minecraft:dirt") then
        turtle.digDown()
        getItem()
        turtle.placeDown()
    end
end

slot = 1

function getItem()
    local details = turtle.getItemDetail(slot)
    while(not details or (details.name ~= "minecraft:dirt" and slot < 16)) do
        slot = slot+1
        details = turtle.getItemDetail(slot)
    end
    turtle.select(slot)
    if (details and details.name ~= "minecraft:dirt") then print "No filler blocks left" end
end

print "Width?"
        y = tonumber(read())
print "Length?"
        x = tonumber(read())
print "Please place fuel in slot 16, filler blocks in other slots. Press any key to start."
        os.pullEvent("key")

x = x-1
y = y-1
refuel()
moveForward()
breakblocks()

left = false

for width = 1, y, 1 do
    for length = 1, x, 1 do
        refuel()
        moveForward()
        breakblocks()
    end
    if left then turtle.turnLeft() else turtle.turnRight()
    end
    refuel()
    moveForward()
    breakblocks()
    if left then turtle.turnLeft() else turtle.turnRight()
    end
    left = not left
end