OO..344.5 |L
OO..3.455 |A
.02.3..55 |Y (2D)
1.223.455 |E
112.344.5 |R
_________
D E P T H
(3rd D) - evaluated left to right (2, not 3)
As soon as 2 numbers would merge, they become a new number. As soon as a number would split (not touching) in one layer, they become 2 different numeric IDs...