For how long did Elly Koss's cystitis last?
SUM(MULTIPLY(365, SUBTRACT(strftime('%Y', STOP), strftime('%Y', START))), MULTIPLY(30, SUBTRACT(strftime('%m', STOP), strftime('%m', START))), SUBTRACT(strftime('%d', STOP), strftime('%d', START))) where DESCRIPTION = 'Cystitis';
SELECT strftime('%J', T2.STOP) - strftime('%J', T2.START) AS days FROM patients AS T1 INNER JOIN conditions AS T2 ON T1.patient = T2.PATIENT WHERE T1.first = 'Elly' AND T1.last = 'Koss' AND T2.description = 'Cystitis'