Create sequence number based on condition

[Sapt86]

I am trying to create a sequence number to enumerate the total number of visits to a service (I cannot delete duplicates because of other variables). 

I already have a variable that indicates if the client presented unique visits. Therefore, the sequence number should enumerate all visits but keep the same number when any client does not present a unique visit. 

I hope you can help me with this since I'm quite new in SAS. Thank you!!

ID	Unique_visit	Total_visits (NEEDED)
1	1	1
1	1	2
1	0	2
2	1	3
2	1	4
3	1	5
3	0	5
3	1	6
4	1	7
4	1	8
4	0	8
4	1	9

[novinosrin · Accepted solution]

data want;
 set have;
 Total_visits +unique_visit;
run;

[Sapt86]

I cannot believe that I was overthinking this. Thank you so much!!

[Reeza]

This requires a RETAIN, which tells SAS to keep the value to the next row. You can explicitly tell SAS to retain the variable but a SUM statement as in novinosrin will add an IMPLICIT retain that will keep the values across the rows. The first variable in the SUM statement is part of the implicit retain.