public Observable<Boolean> tryToLogin(final String api, final String secret) {
        AtomicInteger nonce = new AtomicInteger();
        return login(api, secret, String.valueOf(nonce.get()))
                .map(infoTradeResponse -> {
                    if (infoTradeResponse.getResponseStatus() == BaseTradeResponse.ERROR_STATUS && infoTradeResponse.getResponseError().equals(Constants.NONCE_ERROR)) {
                        Log.d(TAG, "KeysNonceError");
                        throw new KeysNonceError();
                    }
                    else {
                        if (infoTradeResponse.getResponseStatus() == BaseTradeResponse.SUCCESS_STATUS)
                            return true;
                        else return false;
                    }
                })
                .retryUntil(new BooleanSupplier() {
                    int retry = 0;
                    @Override
                    public boolean getAsBoolean() throws Exception {

                        return retry++ > Constants.MAX_RETRY;
                    }
                });
    }