downdig

function tdown()
  turtle.digDown()
  return turtle.down()
end

h=1
t.down()
while tdown(1) do
  h=h+1
  if turtle.getFuelLevel()<100 then
    turtle.select(1)
    turtle.refuel(1)
  end
  for i=1,4 do
    if turtle.detect() then
    dig=true
    for j=2,4 do
      turtle.select(j)
      if turtle.compare() then
        dig=false
        break
      end
    end
    else dig=false end
    if dig then
      turtle.select(1)
      turtle.dig()
      turtle.suck()
    end
    t.left()
  end
end
t.up(h)
turtle.forward()
turtle.forward()
turtle.turnRight()
turtle.forward()
turtle.turnLeft()