<|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
 The sum of 100 numbers is 1990. If we subtract 1 from the first number, add 2 to the second number, subtract 3 from the third number, ..., and add 100 to the 100th number, then the sum of the new numbers is     . 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
2040
The sum of 100 numbers is 1990. If we subtract 1 from the first number, add 2 to the second number, subtract 3 from the third number, ..., and add 100 to the 100th number, then the sum of the new numbers is     .
test