Natural numbers are placed in an infinite grid. Such that the number in each cell is equal to the number of its adjacent cells having the same number. Find the most distinct numbers this infinite grid can have.

(Two cells of the grid are adjacent if they have a common vertex)
1. **Understanding the Problem:**
   - We are given an infinite grid where each cell contains a natural number.
   - The number in each cell is equal to the number of its adjacent cells (including diagonals) that have the same number.
   - We need to find the maximum number of distinct numbers that can be placed in this grid.

2. **Defining Adjacent Cells:**
   - Two cells are adjacent if they share a common vertex. This means each cell has up to 8 neighbors.

3. **Initial Observations:**
   - If a cell contains the number \(a\), then exactly \(a\) of its 8 neighbors must also contain the number \(a\).
   - This implies \(a \leq 8\).

4. **Claim 1:**
   - If \(a \in \mathcal{S}\) and \(|\mathcal{S}| \geq 2\), then \(a \in \{1, 2, 3, 4, 5, 6\}\).
   - **Proof:**
     - If \(a = 8\), then all 8 neighbors must also be 8, leading to the entire grid being filled with 8, contradicting \(|\mathcal{S}| \geq 2\).
     - If \(a = 7\), then exactly one neighbor is not 7. This leads to a contradiction as explained in the solution.

5. **Claim 2:**
   - \(|\mathcal{S}| < 6\).
   - **Proof:**
     - Suppose \(|\mathcal{S}| = 6\). This means numbers 1 to 6 are used.
     - Consider cells with numbers 5 and 6. By the Manhattan distance argument, there must be a contradiction in the arrangement of these cells, as shown in the solution.

6. **Claim 3:**
   - \(|\mathcal{S}| \leq 5\) and equality can hold.
   - **Proof:**
     - From Claims 1 and 2, we have \(|\mathcal{S}| \leq 5\).
     - Construct a grid using numbers \(\{1, 2, 3, 4, 5\}\) that satisfies the given condition.
     - The provided grid construction shows that it is possible to have 5 distinct numbers in the grid.

7. **Conclusion:**
   - The maximum number of distinct numbers that can be placed in the grid is 5.

The final answer is \(\boxed{5}\)