function Forward(i)
  while i>0 do
    turtle.forward()
    i=i-1
  end
end

function PlaceOnLeft()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnRight()
  turtle.place()
  turtle.turnRight()
  turtle.forward()
  turtle.turnLeft()
end

function PlaceOnRight()
  turtle.turnRight()
  turtle.forward()
  turtle.turnLeft()
  turtle.place()
  turtle.turnLeft()
  turtle.forward()
  turtle.turnRight()
end

function Pickup()
  sleep(0.5)
  redstone.setOutput("back",true)
  sleep(0.2)
  redstone.setOutput("back",false)
  sleep(120)
  Forward(7)
  turtle.turnLeft()
  turtle.select(3)
  turtle.place()
  sleep(1)
  turtle.dig()
  turtle.turnLeft()
  Forward(7)
  turtle.turnLeft()
  turtle.turnLeft()
end

function SpawnWither()
  Forward(7)
  turtle.turnLeft()
  turtle.select(1)
  turtle.place()
  turtle.up()
  turtle.place()
  PlaceOnRight()
  PlaceOnLeft()
  turtle.up()
  turtle.select(2)
  PlaceOnRight()
  PlaceOnLeft()
  turtle.place()
  turtle.down()
  turtle.down()
  turtle.turnLeft()
  Forward(7)
  turtle.turnLeft()
  turtle.turnLeft()
  Pickup()
end

while true do
  if redstone.getInput("left") then
    SpawnWither()
    turtle.down()
    turtle.down()
    sleep(10)
    turtle.up()
    turtle.up()
  else
    sleep(10)
  end
  if turtle.getFuelLevel()<10000 then
    print "Low Fuel"
  end
end