<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 The sequence is defined as follows: starting with 2004, 2005, 1, -2004, each term is equal to the sum of its preceding and following terms. Calculate the sum of the first 2005 terms of this sequence. Express your answer as a single integer. Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
2004
The sequence is defined as follows: starting with 2004, 2005, 1, -2004, each term is equal to the sum of its preceding and following terms. Calculate the sum of the first 2005 terms of this sequence. Express your answer as a single integer.
test