Incremental number in Beneficiary registration

In need to set up incremental number on each registered beneficiary. In the registration, I’m avoiding their names instead, each is registered as client_1, client_2, client_3 etc. I have used hidden value that calculate client but I need to have a function that will be assigning 1, 2, 3 in the sequence on how beneficiary are registered e.g. first beneficiary is registered as client_1, second beneficiary is registered as client_2 etc. Any support how this can be done is much appreciated.


You can read about some mechanisms to build these kinds of ids on this wiki