During the interview, five college students said the following: [1] Xuan: "I haven't had any experience in cheating in exams. " [2] Jing: "Xuan lied. " [3] Cheng: "I used to pack nights in Internet cafes. "[4] Tuk:" Cheng is lying. "[5] Hui:" Cheng and Tuk are lying. ". So how many of them are lying? ['.', '.', '.', '.']