computercraft build stairs

term.write("Please enter the width of stair: ")
local w = tonumber(read())

term.write("Please enter the height of stair: ")
local h = tonumber(read())

print("Input the direction of stairs.")
local upOrDown = ""
repeat
  term.write("Please enter up or down: ")
  upOrDown = read()
until (upOrDown == "up") or (upOrDown == "down")

print("Input the way to build stairs.")
local move = ""
repeat
  term.write("Please enter dig or place: ")
  move = read()
until (move == "dig") or (move == "place")

local itemID = 1
for i = 1,h do
  for j = 1,w do
    if move == "place" then
      turtle.select(itemID)
      while (turtle.getItemCount() == 0) do
        itemID = itemID + 1
        if (itemID > 16) then
          break
        end
        turtle.select(itemID)
      end
    end

    if itemID > 16 then
      break
    end

    if move == "place" then
      if upOrDown == "up" then
        turtle.place()
      else
        if j == 1 then
          turtle.forward()
        end
        turtle.placeDown()
      end
    else
      if upOrDown == "up" then
        turtle.dig()
        turtle.digUp()
      else
        turtle.digDown()
        turtle.digUp()
      end
    end

    if j < w then
      if (i % 2 == 1) then
        turtle.turnLeft()
        turtle.dig()
        turtle.forward()
        turtle.turnRight()
      elseif i % 2 == 0 then
        turtle.turnRight()
        turtle.dig()
        turtle.forward()
        turtle.turnLeft()
      end
    end
  end

  if upOrDown == "up" then
    turtle.digUp()
    turtle.up()
    turtle.dig()
    turtle.forward()
  else
    turtle.dig()
    turtle.forward()
    turtle.digDown()
    turtle.down()
  end

  if (itemID > 16) then
    break
  end
end