Weird Shopkeeper

In an imaginary country there is a shopkeeper whose shop has only one item. The initial cost of that item is C. The shopkeeper follows the following approach to change the price of that product. a) For the first 3 days, he increases the price of the item by a value of 1, everyday b) For the next 3 days, he decreases the price by a value of 2, everyday c) For the next 3 days, he increases price