Exam registration problem: help

hi, I am going to attend my CA FINAL exam after 2 and half years of gap. the last two terms I gave was 2.5 years back and couldn't clear the exam. so I don't remember my roll number. now for registration for exam online I have to put roll number of my last two exam. what shall I put over there. I can't proceed further without putting roll number. please help, can I put bogus number or what can I do .