values count
A      2
B      3
C      4
A      5
C      1

Flowable<Response> responseFlowable = Flowable.fromIterable(generateList());
        replayResponseFlowable.toMultimap(response -> response.getValues(), response -> response.getCount()).subscribe(groups-> calculateSum(groups));

    }

    private static void calculateSum(Map<String,Collection<Integer>> groups)
   {
      //iterate over the map and calculate sum for each of the groups.
   }