Stairs Miner [LUA]

textutils.slowPrint("Welcome to the Stair Miner!")
textutils.slowPrint("Please enter the current y level of the turtle now: ")
local input = read()
local inputUp = input
sleep(5)
textutils.slowPrint("Registered!")
sleep(2)
print("Turtle will now start to mine!")
sleep(5)

function start()
  turtle.digDown()
  turtle.forward()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.up()
  turtle.forward()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.up()
  turtle.up()
  turtle.forward()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.up()
end

function stair()
  turtle.dig()
  turtle.forward()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.down()
  turtle.digDown()
  turtle.up()
end

function uptheStairs()
  turtle.forward()
  turtle.up()
end

local bS = input

function backtoSurface()
  turtle.turnRight()
  turtle.turnRight()
  turtle.forward()
  repeat
    uptheStairs()
    bS = bS + 1
  until bS == 63
end

local bedrock = turtle.detect()

start()

repeat
  stair()
  bS = bS - 1
until bS == 6

backtoSurface()
turtle.up()
turtle.forward()
turtle.forward()