Wither

while true do
os.pullEvent("redstone")
if rs.getInput("left",true) then
 for i=1,4 do
  turtle.forward()
 end
 turtle.select(1)
 turtle.place()
 turtle.up()
 turtle.place()
 turtle.turnLeft()
 turtle.forward()
 turtle.turnRight()
 turtle.place()
 turtle.up()
 turtle.select(2)
 turtle.place()
 turtle.turnRight()
 turtle.forward()
 turtle.turnLeft()
 turtle.place()
 turtle.turnRight()
 turtle.forward()
 turtle.turnLeft()
 turtle.down()
 turtle.select(1)
 turtle.place()
 turtle.up()
 turtle.select(2)
 turtle.place()
 turtle.turnLeft()
 turtle.forward()
 turtle.turnRight()
 turtle.down()
 for i=1,4 do
  turtle.back()
 end
 turtle.down()
end
end