Greg has been using drugs for three years. He feels powerless to resist his cravings for drugs. His whole life revolves around his next "high." Nothing else matters to him. He has lost his job. His wife and children have left him, and all he can say is "They didn't understand!" Now he is robbing banks to get money to support his $7,000 per week habit. He is in the ______ stage of drug dependence.