Branch

function forward(aantal, down)
  for i = 1, aantal do
    turtle.dig()
    while not turtle.forward() do
      os.sleep(1)
      turtle.dig()
    end
    if down then
      turtle.digDown()
    end
  end
end

function back()
  while not turtle.back() do
    os.sleep(1)
  end
end

while turtle.getFuelLevel() < 640 do
  term.clear()
  term.setCursorPos(1,1)
  print("You need to refuel")
  io.read()
  turtle.select(1)
  turtle.refuel()
end
while turtle.getItemCount(16) < 20 do
  term.clear()
  term.setCursorPos(1,1)
  print("You need to put 20 torches in slot 16")
  io.read()
end
turtle.select(16)

for i = 1, 20 do
  forward(4,true)
  if i%2 == 0 then
    turtle.placeDown()
  end
  turtle.turnRight()
  forward(5,false)
  for j = 1, 5 do
    back()
  end
  turtle.turnLeft()
end

turtle.turnLeft()
forward(6,false)
for i = 1, 5 do
  back()
end
turtle.digDown()
turtle.turnLeft()

for i = 1, 19 do
  forward(4,true)
  if i%2 == 0 then
    turtle.placeDown()
  end
  turtle.turnRight()
  forward(5,false)
  for j = 1, 5 do
    back()
  end
  turtle.turnLeft()
end
forward(3,true)