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:  4 1 3 6 7 3 4 1 2 9 6 7 5 2 3 7 5 8 3 3 5 9 9 6 4 6
Output: 6 4 6 4 1 3 6 7 3 4 1 2 9 6 7 5 2 3 7 5 8 3 3 5 9 9

Example 2:
Input:  0 0 0 0 0 0 0 0 0 5 6 2 3 5 4 9 5 4 9 2 1 1 5 4 1 8
Output: 4 1 8 0 0 0 0 0 0 0 0 0 5 6 2 3 5 4 9 5 4 9 2 1 1 5

Example 3:
Input:  5 1 5 3 6 7 7 6 3 7 0 0 0 0 0 0 0 0 0 7 5 9 4 5 1 9
Output: 5 1 9 5 1 5 3 6 7 7 6 3 7 0 0 0 0 0 0 0 0 0 7 5 9 4

Below is a test input grid. Predict the corresponding output grid by applying the rule you found.
Input:
6 1 3 9 2 3 9 9 9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 8 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