lumberjack turtle

function up()
    while not turtle.up() do
        turtle.digUp()
    end
end

function cutTree()
    while turtle.compare() do
        turtle.dig()
        up()
    end
    while not turtle.detectDown() do
        turtle.down()
    end
end

function search(dist)
    while dist > 0 do
        if turtle.compare() then
            cutTree()
        elseif not turtle.forward() then
            up()
        else
            dist = dist - 1
            while not turtle.detectDown() do
                turtle.down()
            end
        end
    end
end

local args = {...}
if #args ~= 1 then
    print('Usage: lumberjack <size>')
    return
end

turtle.select(1)
if turtle.getItemCount(1) == 0 then
    print('ERROR: Requires unrefined wood block in slot #1.')
    return
end

for n = 1, args[1], 1 do
    search(n)
    turtle.turnRight()
    search(n)
    turtle.turnRight()
end