Tree Turtle 3.0

turtle.refuel(1)
print("Starting...")

i = 0
a = 0
x = 0
while true do
    x = x+1

    while turtle.detectUp() do
        if turtle.getFuelLevel() < 3 then
            turtle.refuel(3)
        end

        turtle.digUp()
        turtle.up()
        i = i+1

    end

    while i > a do
        if turtle.getFuelLevel() < 3 then
        turtle.refuel(1)
        end
        turtle.down()
        a = a+1
    end

    turtle.dig()
    turtle.forward()
    turtle.turnRight()

    if x == 4 then
        error("Done!")
    end
end