2x2

local function refuel()
    local fuelLevel = turtle.getFuelLevel()
    if fuelLevel == "unlimited" or fuelLevel > 0 then
        return
    end

    local function tryRefuel()
        for n=1,16 do
            if turtle.getItemCount(n) > 0 then
                turtle.select(n)
                if turtle.refuel(1) then
                    turtle.select(15)
                    return true
                end
            end
        end
        turtle.select(1)
        return false
    end

    if not tryRefuel() then
        print( "Add more fuel to continue." )
        while not tryRefuel() do
            sleep(1)
        end
        print( "Resuming Chopping." )
    end
end

function cutdown()
    refuel()
    turtle.dig()
    turtle.digdown()
    turtle.down()
end

function cutup()
    refuel()
    turtle.dig()
    turtle.digUp()
    turtle.up()
end

refuel()
turtle.dig()
turtle.transferTo(15)
turtle.forward()
turtle.select(15)
while turtle.compareUp() do
    cutup()
end
turtle.dig()
refuel()
turtle.forward()
turtle.turnRight()
turtle.dig()
turtle.forward()
turtle.turnRight()
turtle.select(15)
while turtle.compareDown()
    cutdown()
end
print( "Tree Finished" )