<|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
 In an arithmetic progression, the sum of the 5th and 21st term is equal to the sum of the 8th, 15th, and 13th term. Which term of the arithmetic progression is 0? 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
0
In an arithmetic progression, the sum of the 5th and 21st term is equal to the sum of the 8th, 15th, and 13th term. Which term of the arithmetic progression is 0?
test