Find the greatest common factor of $1001$ and $2431.$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Find the greatest common factor of $1001$ and $2431.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
143
Find the greatest common factor of $1001$ and $2431.$
train