KöMaL 2019 B5066

Thirty students were taking an exam in a subject called Tautologics''. The students were sitting down in a classroom, and the teacher asked them a single question, How many of the students sitting in this room are going to fail this exam altogether?'' The students had to name a number, one by one, in a row. After each answer, the teacher immediately announced the result which was either pass'' or fail''. When the exam was over, the Student Union requested an inspection by the School District. If it turns out that any student gave the correct answer but still failed the exam, all the results will be cancelled, and everyone will receive a ``pass'' grade. Is there a strategy for the students to achieve that everyone should pass the exam?