<|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
 Bev is driving from Waterloo, ON to Marathon, ON. She has driven 312 km. She has 858 km still to drive. Calculate the distance Bev must drive to be halfway from Waterloo to Marathon. Express your answer in kilometers (km). 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
273
Bev is driving from Waterloo, ON to Marathon, ON. She has driven 312 km. She has 858 km still to drive. Calculate the distance Bev must drive to be halfway from Waterloo to Marathon. Express your answer in kilometers (km).
test