Combine potatoes, dry au gratin mix, corn with liquid, salsa, and 2 cups water in large saucepan. Heat to a boil; reduce heat. Cover and simmer 25 minutes or until potatoes are tender, stirring occasionally. Add milk, cheese, and olives. Cook until cheese is melted and soup is heated through, stirring occasionally. Garnish with tortilla chips, if desired. Serves 6.