This may work...

term.clear()
term.setCursorPos(1,1)

local function dig()
  repeat until not turtle.digUp()
  turtle.placeDown()
  while not turtle.forward() do
    turtle.dig()
  end
end

local function smartForward()
  while not turtle.forward() do
    if turtle.detect() then
      turtle.dig()
    elseif turtle.attack() then
      print("Aggressive life forms detected!")
    else
      print("Impossible to move forward!")
      return false
    end
  end
  return false
end

local function smartTorch()
  while not turtle.place() do
    if turtle.detect() then
      turtle.dig()
      y = math.floor(x / 8) - 1
    end
  end
end


local function torch()
  turtle.placeDown()
  turtle.select(16)
  turtle.turnRight()
  turtle.digUp()
  turtle.dig()
  smartTorch()
  turtle.place()
  turtle.turnLeft()
  turtle.select(1)
end

print("How Far?")
y = read()
w = math.floor(y * 4)
while true do
  for all = 1, y do

    smartForward()

    dig()

    torch()

  end

   turtle.turnLeft()
   turtle.turnLeft()
  for i = 1, w do
    turtle.forward()
    smartForward()
  end
  turtle.turnRight()
  for z = 3, 14 do
    turtle.select(y)
    turtle.drop()
  end

  turtle.turnLeft()
  turtle.forward()
  turtle.turnLeft()
  turtle.forward()
  turtle.forward()
  turtle.forward()
  turtle.turnLeft()
end