What is $2121_3 - 212_3?$ Express your answer in base 3.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
What is $2121_3 - 212_3?$ Express your answer in base 3.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
1202_3
What is $2121_3 - 212_3?$ Express your answer in base 3.
train