You have obtained 40,000 rank in JEE Main and are interested in pursuing Computer Science Engineering (CSE). It would be difficult to tell you your exact possibilities without knowing your category and category rank. Nevertheless, it will be very difficult for you to get CSE in good colleges if you belong to General category. Even if you have categories, getting top colleges would be tough. You can use the JEE Main college predictor tool by clicking on the following link to know which college you can get admission based on your rank and category. https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer
Hope it helps you.