data have;
input ID time var;
cards;
1 1 1
1 2 1
1 3 0
1 4 1
1 5 1
1 6 1
1 7 0
1 8 1
2 1 1
2 2 1
2 3 0
2 4 0
2 5 1
2 6 1
2 7 0
2 8 1
;
run;
data want;
merge have have(keep=id var rename=(id=_id var=_var) firstobs=2);
retain found .;
if id ne lag(id) then found=.;
if not found and var=0 and id=_id and _var=1 and (id ne lag(id) or (id=lag(id) and lag(var)=1)) then do;found=1;var=1;end;
if var=0 then found=1;
drop found _:;
run;
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