function fuel()
    if turtle.getFuelLevel() < 10 then
        turtle.select(16)
        turtle.refuel(1)
        turtle.select(1)
    end
end

function detectdown()
    turtle.select(15)
    while turtle.compareDown() do
        fuel()
        turtle.digDown()
        turtle.down()
    end
end

function cut()
    fuel()
    turtle.dig()
    turtle.turnRight()
    turtle.dig()
    turtle.turnLeft()
end

fuel()
turtle.dig()
turtle.forward()
turtle.select(15)
while turtle.compareUp() do
    cut()
    fuel()
    turtle.digUp()
    turtle.up()
end
cut()
fuel()
turtle.forward()
turtle.turnRight()
turtle.dig()
turtle.forward()
fuel()
detectdown()