Mine

print("How many branches?")
local input = read()
local output = input-1

function tunnel()

  for i=1,10 do
  while turtle.detect() do
  turtle.dig()
  end
  turtle.forward()
  turtle.digDown()
 end

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

 if turtle.detectDown() == true then
 turtle.up()
 turtle.select(16)
 turtle.placeDown()
 else
 turtle.select(15)
 turtle.placeDown()
 turtle.up()
 turtle.select(16)
 turtle.placeDown()
 end

 for i=1,10 do
 turtle.forward()
 end

 turtle.turnLeft()

 for i=1,3 do
  while turtle.detect() do
  turtle.dig()
  end
  turtle.forward()
  turtle.digDown()
 end

 turtle.turnLeft()

end

function refuel()
 for i=1,14 do
  turtle.select(i)
  turtle.refuel()
 end
end

function home()
 turtle.turnLeft()
 local bal = 1
 for i=1,input do
  turtle.down()
  if turtle.detectDown() == true then
   turtle.up()
   turtle.select(16)
   if bal == 1 then
    turtle.placeDown()
    bal = 2
   elseif bal == 2 then
    bal = 3
   else
    bal = 1
    end
  else
   turtle.select(15)
   turtle.placeDown()
   turtle.up()
   turtle.select(16)
   if bal == 1 then
   turtle.placeDown()
   bal = 2
   elseif bal == 2 then
   bal = 3
   else
   bal =1
   end

  end
  turtle.forward()
  turtle.forward()
  turtle.forward()
 end
 turtle.turnLeft()
 turtle.forward()
 for i=1,14 do
  turtle.select(i)
  turtle.dropDown()
 end
 turtle.turnLeft()
 turtle.turnLeft()
 turtle.forward()
 turtle.down()
end

refuel()
turtle.up()
for i=1,input do
tunnel()
end
home()