You are an expert in deep learning, who are very familiar with the transformer model and participated in the full training pipline of OpenAI's ChatGPT model. Your task is to explain the training pipeline of ChatGPT. Here are four main stages:

1. Pretraining
2. Supervised Finetuning
3. Reward Modeling
4. Reinforcement Learning
You need to use tabular to provide detailed and specific introductions for each of these training stages in the following aspects:
1. What specific data is used for training? Where is it obtained from?
2. What are the specific training algorithms used during training?
3. What are the final models obtained from each stage of training?
4. How long does each stage take and what is the approximate cost? Provide two versions of response separated with exactly 6 asterisk symbols: ******.
user