What is the smallest number after $3456$ whose digits add up to $12$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
What is the smallest number after $3456$ whose digits add up to $12$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
3504
What is the smallest number after $3456$ whose digits add up to $12$?
train