You bought Bitcoin one year ago because you were worried about inflation and you heard it was a good hedge against inflation. At today's price of Bitcoin, your nominal rate of return has been -25.883%. The inflation rate over the last year has been 8.6%. What has been your real rate of return on Bitcoin investment (approximately)? (Your answer should be in percentage terms with at most two decimal places, don't use the percentage sign. E.g., if your answer is -10.23%, type -10.23)