Tun1

x=0
t=turtle
function refuel(n)
  if t.getFuelLevel() <=10 then
    t.select(n)
    t.refuel(1)
  end
end
function fwd(st)
  for i=1,st do
    refuel(1)
    while t.detect() do
      while not(t.dig()) do
        t.attack()
        sleep(0.1)
      end
      sleep(0.2)
    end
    t.digDown()
    while t.detectUp() do
      while not(t.digUp()) do
        t.attackUp()
        sleep(0.1)
      end
    end

    if x>=7 then
      t.select(2)
      t.placeDown()
      x=0
    else
      drop(3)
    end
    while not(t.forward()) do
      t.attack()
      sleep(0.1)
      x=x-1
    end
    x=x+1
  end
end
function drop(sl)
  if t.getItemCount(16) > 0 then
    t.select(sl)
    t.placeDown()
    for i=4, 16 do
      t.select(i)
      t.dropDown()
    end
    t.select(1)
  end
end

print('Length?')
fwd(tonomber(read()))