A conversation between User and Assistant. The user asks a question, and the Assistant solves it. The assistant first thinks about the reasoning process in the mind and then provides the user with the answer.
User: Find the common rule that maps an input grid to an output grid, given the examples below.

Example 1:
Input:  8 9 2 9 5 7 6 0 0 0 0 0 0 0 0 0 0 5 7
Output: 0 0 5 7 8 9 2 9 5 7 6 0 0 0 0 0 0 0 0

Example 2:
Input:  9 4 4 4 3 8 2 5 4 4 1 4 9 8 9 1 8 8 9
Output: 1 8 8 9 9 4 4 4 3 8 2 5 4 4 1 4 9 8 9

Example 3:
Input:  3 2 1 8 9 8 2 6 2 5 7 3 0 0 0 8 7 3 5
Output: 8 7 3 5 3 2 1 8 9 8 2 6 2 5 7 3 0 0 0

Below is a test input grid. Predict the corresponding output grid by applying the rule you found.
Input:
7 8 6 7 8 5 8 3 5 2 1 8 2 3 7 5 3 4 9
Show your work in <think> </think> tags, and return the answer in <answer> </answer> tags with space between each number. For example <answer> 1 3 5 7 </answer>.
Assistant: Let me solve this step by step.
<think>
user