if require("component").isAvailable("generator")
    then
    generator=require("component").generator
end
withg=(generator~=nil)
slots=16
slotstocheck=2
robot=require("robot")
coords={x=0,y=0,z=0,side=1}
extcoords={x=0,y=0,z=0,side=1}
sx={0,1,0,-1}
sy={1,0,-1,0}
--1,2,3,4
--tl  --  coords.side = (coords.side + 3)%4
--tr  --  coords.side = (coords.side + 1)%4
--ta  --  coords.side = (coords.side + 2)%4
--all --  if coords.side == 0 then coords.side =4 end
function go() while not robot.forward() do robot.swing()end coords.x=coords.x + sx[coords.side];coords.y = coords.y + sy[coords.side] end
function godown() while not robot.down() do robot.swingDown()end coords.z = coords.z - 1 end
function goup() while not robot.up() do robot.swingUp()end coords.z = coords.z + 1 end
function check() return robot.count(slots-(slotstocheck-1)) > 0 end
function turnLeft() robot.turnLeft(); coords.side = (coords.side + 3)%4;if coords.side == 0 then coords.side =4 end; end
function turnRight() robot.turnRight(); coords.side = (coords.side + 1)%4; if coords.side == 0 then coords.side =4 end; end
function tosurf()
    extcoords.x=coords.x
    extcoords.y=coords.y
    extcoords.z=coords.z
    extcoords.side=coords.side
    while coords.z ~= 0 do goup() end
    while coords.side ~= 3 do turnRight() end
    while coords.y ~= 0 do go() end
    turnRight();
    while coords.x ~= 0 do go() end
    turnLeft();
end
function back()
    while coords.z ~= extcoords.z do godown() end
    while coords.side~= 1 do turnRight() end
    while coords.y ~= extcoords.y do go() end
    turnRight();
    while coords.x ~= extcoords.x do go() end
    while coords.side ~= extcoords.side do turnRight() end
end
function clearinv()
    alreadyhave=false
    for invcounter=1,slots do
        robot.select(invcounter)
        if withg then
            suc,error=generator.insert()
            if (error=="selected slot does not contain fuel" or alreadyhave) then robot.drop() else alreadyhave=true end
        else
            robot.drop()
        end
    end
    robot.select(1)
    sort()
end
function sort()
    curs=1
    for q=1,slots do
        if robot.count(q) > 0 then robot.select(q);robot.transferTo(curs);curs=curs+1 end
    end
    robot.select(1)
end
function prevent()
    if check() then
        tosurf()
        clearinv()
        back()
    end
end

function digrow(n)
prevent()
robot.swingUp()
prevent()
robot.swingDown()
for k=1,n do
prevent()
go()
prevent()
robot.swingUp()
prevent()
robot.swingDown()
end
end
function digdim(x,y)
godown()
godown()
for n=1,y do
if tl then turnLeft() else turnRight() end
digrow(ex)
if tl then turnRight() else turnLeft() end
tl = not tl
if n==y then print("ok") else go() end
end
turnRight();
turnRight();
tl= not tl
end
x,y,z=...
tl=false
x=x+0
y=y+0
z=z+0
ex=x-1
fullz=(z-z%3)/3
print("Fullz = " .. fullz)
for i=1,fullz do
digdim(x,y)
godown()
end
if fullz*3==z then elseif fullz*3+1==z then goup();goup();digdim(tl,x,y) else goup();digdim(tl,x,y) end
tosurf()
clearinv()