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:  7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 4 2 7 8
Output: 2 7 8 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 4

Example 2:
Input:  7 1 2 4 1 3 0 0 0 6 2 4 3 7 3 8 9 3 9 2 6
Output: 9 2 6 7 1 2 4 1 3 0 0 0 6 2 4 3 7 3 8 9 3

Example 3:
Input:  1 7 5 2 4 7 0 0 5 5 5 1 4 2 8 2 5 4 1 7 2
Output: 1 7 2 1 7 5 2 4 7 0 0 5 5 5 1 4 2 8 2 5 4

Below is a test input grid. Predict the corresponding output grid by applying the rule you found.
Input:
5 5 2 9 0 9 9 3 3 8 2 9 7 4 5 6 3 4 5 4 4
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