Determine if opencourses.gr is currently accessible. If accessible, navigate to the 'Subjects' section and find any available undergraduate courses related to 'Computer Science, Informatics, Telecommunications'. List the titles of the first three courses found, or state if none are found.
Navigate to 'http://opencourses.gr/' If the website is inaccessible (e.g., timeout, error page), state that it is inaccessible and stop. If accessible, locate and click on the 'Subjects' link or equivalent navigation. On the subjects page, find and click on the link for 'Computer Science, Informatics, Telecommunications' (Επιστήμες Υπολογιστών, Πληροφορικής, Τηλεπικοινωνιών). Apply the 'Undergraduate' (Προπτυχιακό) filter under 'Course Level' if available. Extract the titles of the first three courses displayed. If fewer than three, extract all available. If none, state that no courses were found.
Successfully navigate to 'http://opencourses.gr/' OR clearly state that the website is inaccessible. If accessible, successfully navigate to the 'Computer Science, Informatics, Telecommunications' subject page. If accessible, correctly apply the 'Undergraduate' course level filter (if available and necessary for the task). List the exact titles of the first three undergraduate courses found in 'Computer Science, Informatics, Telecommunications', or fewer if not enough are present, or state that no courses were found.