DigStairsDown

turtle.select(16)
turtle.refuel()
turtle.select(1)

function digEverywhere()
  turtle.digDown()
  turtle.digUp()
  turtle.dig()
end

function digStep(count)
  for i=0, count do
    digEverywhere()
    turtle.down()
    digEverywhere()
    turtle.forward()
  end
end

digStep(58)