How can we create formula for sequence number by concatenating based on status value by taking last digit of status value?

Platform discussions Special workflows & use cases
1

We have 3 status columns named L1, L2, and L3.
In L1, values present like L1.1, L1.2, L1.3.
In L2, values present like L2.1, L2.2, L2.3.
In L3, values present like L3.1, L3.2, L3.3.

image

In above column L3 is under L2 and L2 is under L1. So here we need to maintain a hierarchy like this:

image

So we need to concatenate all these 3 columns in one formula to get an exact sequence number.
But when we normally concatenate these above 3 columns we will get an empty word so for that, I used the SUBSTITUTE function. And for taking the last digit value I used the RIGHT function.

But we want this sequence number in different formats like we want only the last digit of this value after concatenating like shown in below picture (Sequence Number column).
image

So, Suggest a formula to create sequence number.