Blast Furnace

function iron()
  turtle.select(2)
  b = turtle.getItemCount(2)
  if b > 1 and not turtle.drop(b-1) then
   os.sleep(5)
  end
end

function charcoal()
   turtle.select(1)
   c = turtle.getItemCount(1)
   if c > 1 and not turtle.drop(c-1) then
    os.sleep(5)
 end
end

function steel()
  turtle.select(4)
  turtle.suck()
end

function dust()
  turtle.select(3)
  turtle.suck()
end

function unload()
for i = 3,4 do
 a = turtle.getItemCount(i)
 turtle.select(i)
 turtle.dropDown(a-1)
 end
end

function main()
 while true do
  unload()
  iron()
  charcoal()
  steel()
  dust()
  sleep(60)
 end
end

main()