function digAndMove()
    if turtle.compare() then
        turtle.dig()
        turtle.forward()
        mine()
        turtle.back()
    end
end

function digUpAndMove()
    if turtle.compareUp() then
        turtle.digUp()
        turtle.up()
        mine()
        turtle.down()
    end
end

function digDownAndMove()
    if turtle.compareDown() then
        turtle.digDown()
        turtle.down()
        mine()
        turtle.up()
    end
end

function mine()

    for i=1,4 do
        digAndMove()
        turtle.turnLeft()
    end

    digUpAndMove()
    digDownAndMove()

end

turtle.select(1)
mine()