code: public InputStream download(final ProblemInput input, final int attempt) throws IOException {
  		final String filename = buildFilename(input, attempt);
  		final StringBuilder urlBuilder = new StringBuilder();
  		urlBuilder.append(round.getURL())
  			.append(DO)
  			.append(COMMAND_PARAMETER)
  			.append(DOWNLOAD_COMMAND)
  			.append(PROBLEM_PARAMETER)
  			.append(input.getProblem().getId())
  			.append(FILENAME_PARAMETER)
  			.append(filename)
  			.append(INPUT_ID_PARAMETER)
  			.append(input.getNumber())
  			.append(CSRF_PARAMETER)
  			.append(values.getURLEncodedToken())
  			.append(AGENT_PARAMETER)
  			.append(DEFAULT_AGENT);
  		final HttpRequest request = executor.getRequest(urlBuilder.toString());
  		final HttpResponse response = request.execute();
  		return response.getContent();
  	}
docs: <p>Downloads and returns the stream of the
  input file associated to the given problem
  <tt>input</tt>.</p>
  
  @param input Input to download file from.
  @param attempt Attempt number.
  @return Stream to read which contains our downloaded file data.
  @throws IOException If any error occurs while downloading the file.