turtle.forward()
while turtle.detectDown() == false do
    turtle.placeDown()
    if turtle.detect() == true then
        turtle.dig()
    else
        turtle.forward()
    end
end
turtle.turnRight()
if turtle.detect() == true then
    turtle.dig()
    turtle.forward()
else
    turtle.forward()
end
if turtle.detectDown() == false then
    turtle.turnLeft()
    while turtle.detectDown() == false do
        if turtle.detect() == false then
            turtle.dig()
            turtle.forward()
        else
            turtle.forward()
        end
    end
    turtle.turnRight()
    turtle.turnRight()
else
    turtle.turnRight()
    while turtle.detectDown() == true do
        turtle.forward()
    end
end
while turtle.detectDown() == false do
    turtle.forward()
    turtle.placeDown()
end