Thank you for your rejection letter. After careful consideration, I regret to inform you that I am unable to accept your refusal to offer me a position.
This year I have been particularly fortunate in receiving an unusually large number of rejection letters. With such a varied and promising field of candidates it is impossible for me to accept all refusals.
Despite your outstanding qualifications and previous experience in rejecting applicants, I find that your rejection does not meet my needs at this time. Therefore, I will assume the position in your organization this August. I look forward to seeing you then.
Best of luck in rejecting future applicants.
Oh, and did you like my chalkboard message? You can create one of your own if you ask nicely.