local sSnow = 1
local sPlate = 5
local sRep = 9
local sPist = 13

function fwd()
  while not turtle.forward() do turtle.attack() end
end

function placeSnow(dir)
  while turtle.getItemCount(sSnow) <= 0 and sSnow <= 16 do
    sSnow = sSnow + 1
  end
  if sSnow >= sPlate then
    error("Out of snow")
  end

  turtle.select(sSnow)
  if dir == -1 then
    turtle.placeDown()
  elseif dir == 1 then
    turtle.placeUp()
  else
    turtle.place()
  end
end

function placePlate(dir)
  while turtle.getItemCount(sPlate) <= 0 and sPlate <= 16 do
    sPlate = sPlate + 1
  end
  if sPlate >= sRep then
    error("Out of pressure plates")
  end

  turtle.select(sPlate)
  if dir == -1 then
    turtle.placeDown()
  elseif dir == 1 then
    turtle.placeUp()
  else
    turtle.place()
  end
end

function placeRep(dir)
  while turtle.getItemCount(sRep) <= 0 and sRep <= 16 do
    sRep = sRep + 1
  end
  if sRep >= sPist then
    error("Out of repeaters")
  end

  turtle.select(sRep)
  if dir == -1 then
    turtle.placeDown()
  elseif dir == 1 then
    turtle.placeUp()
  else
    turtle.place()
  end
end

function placePist(dir)
  while turtle.getItemCount(sPist) <= 0 and sPist <= 16 do
    sPist = sPist + 1
  end
  if sPist > 16 then
    error("Out of pistons")
  end

  turtle.select(sPist)
  if dir == -1 then
    turtle.placeDown()
  elseif dir == 1 then
    turtle.placeUp()
  else
    turtle.place()
  end
end

function segment()
  for i = 1, 13 do
    placeSnow(-1)
    fwd()
  end

  turtle.back()
  turtle.turnRight()
  fwd()
  turtle.turnRight()

  for i = 1, 13 do
    turtle.turnRight()
    fwd()
    fwd()
    fwd()
    placePist(1)
    turtle.back()
    placeSnow(-1)
    placeSnow(0)
    placeSnow(1)
    turtle.back()
    placeRep(0)
    turtle.back()
    placePlate(0)
    turtle.turnLeft()
    fwd()
  end

  turtle.turnLeft()
  turtle.back()
  turtle.down()

  for i = 1, 4 do
    placeSnow(1)
    fwd()
  end
end

turtle.up()

segment()

turtle.turnLeft()
fwd()
turtle.up()

for i = 1, 12 do
  fwd()
end

turtle.turnLeft()
fwd()
turtle.turnLeft()

segment()