Answer the following Q with stream of consciousness. Passage: Big Brother is a game show in which a group of contestants, referred to as HouseGuests, live in a custom-built "house" (actually a set built on a CBS stage in Los Angeles, Stage 18 in recent editions), constantly under video surveillance. While in the house, the contestants are completely isolated from the outside world, meaning no phone, television, internet, magazines, newspaper, or contact with those not in the house. This rule could be broken, however, in the event of a medical injury, a family emergency or death. The format of the series is mainly seen as a social experiment, and requires HouseGuests to interact with others who may have differing ideals, beliefs, and prejudices. While a competition, the series allows viewers to witness the relationships formed in the house and the behavior of the HouseGuests. Though locked in the house, the HouseGuests are free to quit the game, though will not be allowed entry back into the house. Should a HouseGuest break the rules of the game, they could be expelled from the house, and unable to return. The contestants compete for a grand prize of $500,000.

Question: Based on this passage, where is the big brother house in usa?
This is the relevant information: Big Brother is a game show in which a group of contestants, referred to as HouseGuests, live in a custom-built "house" (actually a set built on a CBS stage in Los Angeles, Stage 18 in recent editions), constantly under video surveillance. Therefore, the final answer is a CBS stage in Los Angeles , Stage 18 in recent editions.