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:  2 3 1 7 0 0 0 0 0 0 0 0 0 9 5 6 6 7 1 9 4
Output: 3 1 7 0 0 0 0 0 0 0 0 0 9 5 6 6 7 1 9 4 2

Example 2:
Input:  2 4 6 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 2
Output: 4 6 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 2 2

Example 3:
Input:  6 4 8 2 9 9 0 1 6 5 8 4 8 6 8 7 2 6 1 9 1
Output: 4 8 2 9 9 0 1 6 5 8 4 8 6 8 7 2 6 1 9 1 6

Below is a test input grid. Predict the corresponding output grid by applying the rule you found.
Input:
4 6 6 4 6 1 8 6 5 2 0 0 0 0 0 0 0 0 0 8 5
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