$$7$$ friends - $$A$$、$$B$$、$$C$$、$$D$$、$$E$$、$$F$$、$$G$$, went for dinner togther. In the restaurant, there is a round table with 7 seats with their names being placed at the back of the chairs. They entered the restaurant in a random order. They would choose not to sit on their own personal chair if it is possible. How many different ways of seating arrangments are there? 
Overseas Competition->Knowledge Point->Calculation Modules->Comparing, Ordering and Estimating