smartexc

function clear()
	digUp = true
	digDown = true
	for i = 2, 4 do
		turtle.select(i)
		if(turtle.compareUp()) then digUp = false end
		if(turtle.compareDown()) then digDown = false end
	end
	turtle.select(1)
	if(digUp) then turtle.digUp() end
	if(digDown) then turtle.digDown() end
end

function move()
	if (turtle.getItemCount(16) ~= 0) then
		dropItems()
	end
	if(turtle.getFuelLevel() == 0) then
		error("Out of fuel")
	end
	while (not turtle.forward()) do
		turtle.dig()
	end
end

function right()
	turtle.turnRight()
end

function left()
	turtle.turnLeft()
end

function down3()
	for num = 1, 3 do
		turtle.digDown()
		turtle.down()
	end
end

function outer()
	for num = 1, 3 do
		for num = 2, size do
			clear()
			move()
		end
		right()
	end
end

function inner()
	peaks = (size / 2) - 1
	for num = 1, peaks do
		ascend()
		descend()
	end
	clear()
	move()
	right()
end

function ascend()
	clear()
	move()
	right()
	for num = 3, size do
		clear()
		move()
	end
	left()
end

function descend()
	clear()
	move()
	left()
	for num = 3, size do
		clear()
		move()
	end
	right()
end

function dropItems()
        right()
        right()
        while (not turtle.place()) do
                turtle.dig()
        end
        for num = 5, 16 do
                turtle.select(num)
                turtle.drop()
        end
		turtle.select(1)
		turtle.dig()
        left()
        left()
end

------------------------

local args = { ... }
size = tonumber(args[1])

oddSide = false
if(size % 2 == 1) then
	oddSide = true
end

if(turtle.getItemCount(1) == 0) then
        error("Place endchest in slot 1 and try again")
end

if(turtle.getItemCount(2) == 0 or turtle.getItemCount(3) == 0 or turtle.getItemCount(4) == 0) then
        error("Place stone, dirt, gravel in slots 2-4")
end

while(true) do
	outer()
	inner()
	down3()
end