<|im_start|>system
You are a helpful assistant. You first thinks about the reasoning process in the mind and then provides the user with the answer.<|im_end|>
<|im_start|>user
The target is 2401, and the numbers I obtained are 13, 14, 15, and 1. You need to use these numbers and basic arithmetic operations (+, -, ×, ÷) to produce the target number. Each number in the list can only be used once per equation, and you must show your work in <think>.....</think> tags. If all attempts fail to produce the target number, you must provide an explanation.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>