Print Elements on buffer, Flowable rxJava

Question

How to print elements in buffer when using backpressure:

 Flowable.range(1, 1000)
                .onBackpressureBuffer(20, () ->{}, BackpressureOverflowStrategy.DROP_OLDEST)
                .onBackpressureDrop(v -> System.out.println("Dropped.. :" + v))
                .delay(0, TimeUnit.MILLISECONDS, Schedulers.io())
                .doOnNext(value -> System.out.println("got " + value))
                .map(value -> {
                    try {
                        TimeUnit.SECONDS.sleep(1);
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    return value;
                })
                .observeOn(Schedulers.newThread(),false, 20)
                .subscribe(
                        value -> System.out.println("handled:  " + value),
                        Throwable::printStackTrace,
                        () -> System.out.println("completed")
                );
        sleep(10000);

the output:
got 1
Dropped.. :21
Dropped.. :22
Dropped.. :23
Dropped.. :24
Dropped.. :25
.
.
.

I want
got 1
elements in buffer: 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20
Dropped.. :21
.
.
.

I do not know if that is possible or not. Please help I'am new in reactive programming
Thanks