A 16-year-old patient throughout the last year presents with gradual changes in his behavior. He started preferring solitude and has lost interest in his friends and studies. He became indifferent to his family and rude without provocation, started speaking and laughing with himself. All the questions he answers laconically. He considers himself to be healthy, but tired, says that he thinks about writing a book titled «Projection of mankind onto the plane of the universe», and carries around a notebook with pages that are filled with numerous identical crosses. Make the right diagnosis: