Solve the Sudoku puzzles by filling in the missing numbers so that each row, column, and 3x3 box contains all digits from 1 to 9.

To solve these Sudoku puzzles, we need to fill in the empty squares so that every row, every column, and every 2x3 box contains the numbers 1 through 6 exactly once.

Here is the step-by-step solution for both puzzles.

Puzzle 1 (Top Grid)

Step 1: Look at Row 2
The numbers currently in Row 2 are `3`, `5`, `4`. The missing numbers are `1`, `2`, `6`.
* Look at the first empty square in Row 2 (Column 1). Column 1 already has a `1` (in Row 3) and a `3` (in Row 1). It doesn't have a `2` or `6` yet. Let's look closer.
* Actually, let's look at Row 3. It has `1`, `4`, `2`. Missing are `3`, `5`, `6`.
* The last square in Row 3 (Column 6) is in a column that already has `4`, `1`, `5`. Wait, Column 6 has `4` (Row 2), `5` (Row 4).
* Let's try a simpler spot. Look at Box 1 (Top Left). It has `5`, `3`, `4`. The bottom row of this box is part of Row 3 which starts with `1`, `4`, `2`. So the remaining cells in Box 1 are Row 2 Col 1, Row 2 Col 2, Row 3 Col 1, Row 3 Col 2... wait, the boxes are 2 rows high and 3 columns wide.
* Box 1 (Rows 1-2, Cols 1-3): Contains `5, 3, 4` (Row 1). Row 2 has `?, ?, ?`. The numbers missing in this box are `1, 2, 6`.
* Box 2 (Rows 1-2, Cols 4-6): Contains `3, 5, 4` (Row 1) and `?, 2, 4, 1`... wait, Row 2 is `?, ?, ?, 3, 5, 4`? No, the image shows Row 2 as `[blank] [blank] [blank] | 3 5 4`.
* So Row 2 ends with `3, 5, 4`. The first three blanks must be `1, 2, 6`.
* Look at Column 1. It has `5` (R1), `1` (R3), `3` (R5).
* Look at Column 2. It has `3` (R1), `4` (R3), `6` (R5).
* Look at Column 3. It has `4` (R1), `2` (R3), `5` (R5).

Let's restart with a very clear logical path for Puzzle 1.

Puzzle 1 Analysis:

Row 2: The given numbers are `3, 5, 4` in the right half. The left half is empty. The missing numbers for the whole row are `1, 2, 6`.
* Cell (2,1): Column 1 has `5, 1, 3`. So it can't be `1` or `3` or `5`. It needs to be `2` or `6`.
* Cell (2,2): Column 2 has `3, 4, 6`. So it can't be `6`. It must be `1` or `2`.
* Cell (2,3): Column 3 has `4, 2, 5`. So it can't be `2`. It must be `1` or `6`.

Let's look at Row 4: `?, ?, ? | 6, 3, 5`. Missing numbers are `1, 2, 4`.
* Cell (4,3): Column 3 has `4, 2, 5`. So it can't be `2` or `4`. It MUST be `1`.
* So Cell (4,3) = 1.
* Now Row 4 missing are `2, 4`.
* Cell (4,1): Column 1 has `5, 1, 3`. It can be `2` or `4`.
* Cell (4,2): Column 2 has `3, 4, 6`. It has a `4`. So Cell (4,2) cannot be `4`. It MUST be `2`.
* So Cell (4,2) = 2.
* Therefore, Cell (4,1) = 4.
* Row 4 is now: `4, 2, 1, 6, 3, 5`.

Now back to Row 2 (`?, ?, ?, 3, 5, 4`). Missing `1, 2, 6`.
* Cell (2,2): Column 2 now has `3, ?, 4, 2, 6, ?`. We just put `2` in (4,2). Column 2 has `3` (R1), `4` (R3), `2` (R4), `6` (R5). The missing numbers in Col 2 are `1, 5`. But Row 2 needs `1, 2, 6`. The intersection is `1`.
* So Cell (2,2) = 1.
* Remaining for Row 2 are `2, 6`.
* Cell (2,1): Column 1 has `5` (R1), `1` (R3), `4` (R4), `3` (R5). Missing in Col 1 are `2, 6`.
* Cell (2,3): Column 3 has `4` (R1), `2` (R3), `1` (R4), `5` (R5). Missing in Col 3 are `3, 6`. But Row 2 needs `2` or `6`. The common number is `6`.
* So Cell (2,3) = 6.
* Therefore, Cell (2,1) = 2.
* Row 2 is now: `2, 1, 6, 3, 5, 4`.

Now fill in the rest of Column 1: `5, 2, 1, 4, 3, ?`. Missing is `6`.
* So Cell (6,1) = 6.

Now fill in the rest of Column 2: `3, 1, 4, 2, 6, ?`. Missing is `5`.
* So Cell (6,2) = 5.

Now fill in the rest of Column 3: `4, 6, 2, 1, 5, ?`. Missing is `3`.
* So Cell (6,3) = 3.

Now look at Row 6: We have `6, 5, 3` on the left. The right side is `?, ?, ?`. The full row needs `1, 2, 4`.
* Cell (6,4): Column 4 has `3` (R1), `6` (R4). Also R2C4=3, R3C4=?, R5C4=?.
* Let's check Column 4. Current values: R1=`3`, R2=`3` (Wait, R2C4 is 3 from the prompt). R4=`6`.
* Let's re-read the grid carefully.
* R1: `5 3 4 | 3 5 4` -> This is invalid Sudoku if taken literally as a full row. Ah, the vertical line separates two 3x2 blocks? No, standard Sudoku is 9x9 or 6x6. This is 6x6. The thick lines divide it into 2x3 regions.
* Region 1 (Top Left): Rows 1-2, Cols 1-3.
* Region 2 (Top Right): Rows 1-2, Cols 4-6.
* Region 3 (Mid Left): Rows 3-4, Cols 1-3.
* Region 4 (Mid Right): Rows 3-4, Cols 4-6.
* Region 5 (Bot Left): Rows 5-6, Cols 1-3.
* Region 6 (Bot Right): Rows 5-6, Cols 4-6.

Let's re-evaluate based on Regions.

Puzzle 1 Re-solve:

Region 2 (Top Right): Cells are R1C4-6 (`3,5,4`) and R2C4-6 (`3,5,4`?? No, the image shows `3 5 4` in R1 and `? 2 4 1`? No.
Image Text:
Row 1: `5 3 4 | 3 5 4` -> This implies the pre-filled numbers are `5,3,4` and `3,5,4`. This is impossible because `3,4,5` repeat in the row.
*Correction*: Looking closely at the image, Row 1 is `5 3 4` then a gap, then `3 5 4`. Wait, no. The numbers `3 5 4` are in the second block.
Let's assume the standard layout:
R1: `5 3 4 | _ _ _` AND `_ _ _ | 3 5 4`? No.
The text says:
`5 3 4 | 3 5 4` is likely `5 3 4` in the first 3 cols, and `3 5 4` in the next 3? That would mean Row 1 is `5 3 4 3 5 4`. Duplicate 3s, 4s, 5s. That's not right.

Let's look at the spacing again.
Row 1: `5 3 4` [space] `3 5 4`
Row 2: [space] [space] [space] `3 5 4` ?? No, Row 2 has `2 4 1` at the end?
Let's read the numbers explicitly from the grid positions.

Grid 1:
R1: `5, 3, 4, _, _, _` ? No, the `3 5 4` is aligned under the right side.
Actually, usually these worksheets have some numbers filled.
R1: `5, 3, 4` in cols 1-3. Cols 4-6 are empty? Or is `3 5 4` in cols 4-6?
If R1 is `5 3 4 3 5 4`, it's broken.

Let's look at Row 2: `_ _ _ | 3 5 4`? No, looking at the second row of numbers in the top block:
It looks like:
R1: `5 3 4 | . . .`
R2: `. . . | 3 5 4` -- Wait, the `3 5 4` is on the right.
BUT, looking at the third row of the top block (which is actually Row 3 of the grid):
R3: `1 4 2 | . . .`
R4: `. . . | 6 3 5` ?? No, `6 3 5` is on the right.

Let's try this interpretation:
Top Block (Rows 1-2):
R1: `5 3 4 | _ _ _`
R2: `_ _ _ | 3 5 4` -> This puts 3,5,4 in R2C4-6.

Middle Block (Rows 3-4):
R3: `1 4 2 | _ _ _`
R4: `_ _ _ | 6 3 5` -> This puts 6,3,5 in R4C4-6.

Bottom Block (Rows 5-6):
R5: `3 6 5 | _ _ _`
R6: `_ _ _ | _ _ _`

Let's check if this works.
Col 4: Has `3` (from R2), `6` (from R4).
Col 5: Has `5` (from R2), `3` (from R4).
Col 6: Has `4` (from R2), `5` (from R4).

Let's solve Region 2 (Top Right, R1-2, C4-6).
Existing numbers in Region 2: `3, 5, 4` (from R2).
Missing numbers: `1, 2, 6`.
These must go in R1C4, R1C5, R1C6.
* Check Col 4: R2C4=3, R4C4=6. So R1C4 cannot be 6.
* Check Col 5: R2C5=5, R4C5=3.
* Check Col 6: R2C6=4, R4C6=5.

Let's look at Row 1.
R1 Left is `5, 3, 4`. Missing `1, 2, 6`.
So R1C4, R1C5, R1C6 must be `1, 2, 6`.

Let's look at Col 4.
Values present: R2=3, R4=6.
R1C4 is one of `1, 2, 6`. Since Col 4 has a 6 (at R4), R1C4 cannot be 6.

Let's look at Col 5.
Values present: R2=5, R4=3.
R1C5 is one of `1, 2, 6`.

Let's look at Col 6.
Values present: R2=4, R4=5.
R1C6 is one of `1, 2, 6`.

This path is tricky without more constraints. Let's look at Region 4 (Mid Right, R3-4, C4-6).
Existing: `6, 3, 5` (from R4).
Missing: `1, 2, 4`.
These go in R3C4, R3C5, R3C6.
* R3 Left is `1, 4, 2`. So R3 already has `1, 2, 4`.
* Therefore, R3C4, R3C5, R3C6 MUST be `1, 2, 4` in some order.
* Check Col 4: R2C4=3, R4C4=6. R3C4 needs to be `1, 2, or 4`.
* Check Col 5: R2C5=5, R4C5=3. R3C5 needs to be `1, 2, or 4`.
* Check Col 6: R2C6=4, R4C6=5. R3C6 cannot be 4 (because R2C6 is 4). So R3C6 is `1` or `2`.

Let's look at Col 6 overall.
R2C6 = 4.
R4C6 = 5.
R3C6 is `1` or `2`.
R1C6 is `1, 2, or 6`.
R5C6 is ?
R6C6 is ?

Let's step back and look at Column 1.
R1C1=5, R3C1=1, R5C1=3.
Missing: `2, 4, 6`.
Cells: R2C1, R4C1, R6C1.
* R2C1 is in Region 1. Region 1 (R1-2, C1-3) has `5,3,4` in R1. Missing `1,2,6`.
* R2C1 must be `1, 2, or 6`. But Col 1 needs `2, 4, 6`. Intersection: `2, 6`.
* R4C1 is in Region 3. Region 3 (R3-4, C1-3) has `1,4,2` in R3. Missing `3,5,6`.
* R4C1 must be `3, 5, or 6`. But Col 1 needs `2, 4, 6`. Intersection: `6`.
* So R4C1 = 6.

Now Col 1 missing are `2, 4`. Cells R2C1, R6C1.
* R2C1 must be `2` or `6` (from Region 1 logic above). Since 6 is used in R4C1, and R2C1 can't be 4 (Region 1 missing 1,2,6), R2C1 MUST be 2.
* So R2C1 = 2.
* Therefore, R6C1 = 4.

Now we have Col 1: `5, 2, 1, 6, 3, 4`.

Now Region 1 (Top Left):
R1: `5, 3, 4`
R2: `2, ?, ?`
Missing in Region 1: `1, 6`.
Cells: R2C2, R2C3.
* Check Col 2: R1C2=3, R3C2=4, R5C2=6.
* R2C2 cannot be 6 (because R5C2 is 6).
* So R2C2 = 1.
* Therefore, R2C3 = 6.

So Row 2 is: `2, 1, 6, 3, 5, 4`. (Matches our earlier deduction!)

Now Region 3 (Mid Left):
R3: `1, 4, 2`
R4: `6, ?, ?` (We found R4C1=6).
Missing in Region 3: `3, 5`.
Cells: R4C2, R4C3.
* Check Col 2: Has `3` (R1), `1` (R2), `4` (R3), `6` (R5). Missing `2, 5`.
* R4C2 must be `3` or `5`. Col 2 needs `2` or `5`. Intersection: `5`.
* So R4C2 = 5.
* Therefore, R4C3 = 3.

So Row 4 is: `6, 5, 3, 6, 3, 5`? Wait.
R4 Left is `6, 5, 3`.
R4 Right was given as `6, 3, 5`? No, the prompt said R4 right is `6 3 5`.
If R4 is `6 5 3 | 6 3 5`, there are duplicate 6s, 3s, 5s in the row.

Let's re-read the image for Row 4 Right Side.
Image: ` | 6 3 5`
My calculated Left Side: `6 5 3`.
Conflict! R4C1=6 and R4C4=6.

Where did I go wrong?
"R4C1 must be 3, 5, or 6. But Col 1 needs 2, 4, 6. Intersection: 6."
Let's re-verify Col 1 needs.
Col 1 Given: R1=5, R3=1, R5=3.
Missing: 2, 4, 6.
Region 3 (R3-4, C1-3) contains R3(`1,4,2`). Missing `3,5,6`.
So R4C1, R4C2, R4C3 are `3,5,6`.
R4C1 is in Col 1. Col 1 needs `2,4,6`.
Intersection of `{3,5,6}` and `{2,4,6}` is `6`.
So R4C1=6 is correct.

Why does R4 Right have a 6?
Maybe my reading of "R4 Right is 6 3 5" is wrong?
Let's look at the image again.
Row 4: `[blank] [blank] [blank] | 6 3 5`
Yes, it looks like 6 3 5.

Is it possible the puzzle is flawed? Or did I misidentify the region boundaries?
Standard 6x6 Sudoku regions are 2x3 (2 rows, 3 columns).
Region 3 is Rows 3-4, Cols 1-3.
Region 4 is Rows 3-4, Cols 4-6.

If R4C1=6 and R4C4=6, that violates the row rule.

Let's re-check Col 1 Given numbers.
R1: 5
R3: 1
R5: 3
Are there any others?
R2 is blank in Col 1.
R4 is blank in Col 1.
R6 is blank in Col 1.

Let's re-check Region 3 Given numbers.
R3: `1 4 2`.
R4: Blank Blank Blank.
So Region 3 missing are `3, 5, 6`. Correct.

Let's re-check Col 1 constraints.
R1=5, R3=1, R5=3.
Missing `2, 4, 6`. Correct.

Intersection for R4C1:
Must be in `{3,5,6}` (Region constraint) AND `{2,4,6}` (Col constraint).
Only `6` fits.

So R4C1 MUST be 6.

If the printed puzzle has a 6 in R4C4, the puzzle is invalid OR I am misreading the number in R4C4.
Could R4C4 be a `b`? No.
Could it be a `5`? `6 3 5`.
Could R4C1 be something else?

Let's look at Col 2.
R1=3, R3=4, R5=6.
Missing `1, 2, 5`.
R4C2 is in Region 3 (needs `3,5,6`).
Intersection of `{3,5,6}` and Col 2 missing `{1,2,5}` is `5`.
So R4C2=5.

Then R4C3 must be `3` (last one for Region 3).
So Row 4 Left is `6, 5, 3`.

If Row 4 Right is `6, 3, 5`, then Row 4 is `6, 5, 3, 6, 3, 5`.
Duplicates: 6, 5, 3.

Hypothesis: The number in R4C4 is NOT 6.
Looking at the crop... it looks like a `6`.
Is it possible the number in R5C1 is not 3?
R5: `3 6 5`. Looks like 3.

Is it possible the number in R1C1 is not 5?
R1: `5 3 4`. Looks like 5.

Is it possible the regions are 3x2 (3 rows, 2 columns)?
If regions are 3x2:
Region 1: R1-3, C1-2.
Region 2: R1-3, C3-4.
Region 3: R1-3, C5-6.
Region 4: R4-6, C1-2.
...
Let's test this.
Region 1 (R1-3, C1-2):
Cells:
R1: 5, 3
R2: ?, ?
R3: 1, 4
Numbers present: 1, 3, 4, 5. Missing: 2, 6.
So R2C1, R2C2 are 2, 6.

Region 2 (R1-3, C3-4):
Cells:
R1: 4, ? (R1C4 is blank in this model? No, R1 is `5 3 4 | 3 5 4`. If regions are 3x2, the vertical line is just visual separation for the 2x3 blocks usually. But if the blocks are 3x2, the lines would be horizontal after row 3.)
The thick lines in the image are clearly after Row 2 and Row 4. And after Col 3.
This confirms 2x3 regions (2 rows high, 3 columns wide).

So my initial analysis holds. The puzzle seems to have a conflict IF R4C4 is 6.

Let's look really closely at R4C4.
It is in the second block of the middle row.
Middle Row Blocks:
Left: `1 4 2` / `? ? ?`
Right: `? ? ?` / `6 3 5`

Wait! Look at Row 3 Right Side. It is BLANK.
Look at Row 4 Right Side. It is `6 3 5`.

Is it possible R4C4 is a `G`? No.
Is it possible R4C1 is not 6?

Let's re-read Col 1.
R1: 5
R2: ?
R3: 1
R4: ?
R5: 3
R6: ?

Let's re-read Region 3 (R3-4, C1-3).
R3: 1, 4, 2.
R4: ?, ?, ?.
Missing: 3, 5, 6.

Let's re-read Col 1.
Present: 5, 1, 3.
Missing: 2, 4, 6.

R4C1 must be in {3,5,6} AND {2,4,6}. -> 6.

There is no way out. R4C1 is 6.
If R4C4 is 6, the puzzle is broken.

Alternative: Did I misread R5C1?
R5: `3 6 5`.
If R5C1 was `2`, then Col 1 has 5,1,2. Missing 3,4,6.
R4C1 intersection {3,5,6} and {3,4,6} is {3,6}.
If R4C1=3, then R4C2/C3 are 5,6.

But R5C1 clearly looks like a 3.

Alternative: Did I misread R1C1?
If R1C1=6? No, looks like 5.

Alternative: Did I misread the Region 3 contents?
R3: `1 4 2`.

Let's assume there is a typo in my reading of R4C4.
What if R4C4 is `2`?
Then Row 4 Right is `2 3 5`.
Row 4 Left is `6 5 3`.
Row 4: `6 5 3 2 3 5`. Duplicate 3, 5.

What if R4C4 is `1`?
Row 4 Right `1 3 5`.
Row 4 Left `6 5 3`.
Row 4: `6 5 3 1 3 5`. Duplicate 3, 5.

What if R4C4 is `4`?
Row 4 Right `4 3 5`.
Row 4 Left `6 5 3`.
Row 4: `6 5 3 4 3 5`. Duplicate 3, 5.

The duplicates come from the Left Side calculation `6 5 3`.
R4C2=5, R4C3=3.
Why?
R4C2: Region 3 needs 3,5,6. Col 2 needs 1,2,5 (if R1=3, R3=4, R5=6).
Intersection is 5.

Is R5C2 definitely 6?
R5: `3 6 5`. Yes.
Is R1C2 definitely 3?
R1: `5 3 4`. Yes.
Is R3C2 definitely 4?
R3: `1 4 2`. Yes.

So Col 2 has 3,4,6. Missing 1,2,5.
R4C2 must be 5.

So R4 Left IS `6 5 3`.
This contains a 3 and a 5.
Therefore, R4 Right CANNOT contain a 3 or a 5.
But R4 Right is `6 3 5`. It contains 3 and 5.

Conclusion: The puzzle as printed contains a contradiction or I am blind.

WAIT. Look at Row 4 Right again.
`6 3 5`.
Look at Row 2 Right.
`3 5 4`.

Is it possible the rows are shifted?
No.

Let's look at the Second Puzzle to see if I can solve that one cleanly. Maybe the first one has a typo in the book.

### Puzzle 2 (Bottom Grid)

Given:
R1: `4 . 2 | . 1 .`
R2: `5 . 1 | . 3 .`
R3: `. 4 . | 1 . 2`
R4: `. 1 . | 3 . 6`
R5: `1 . 4 | . 6 .`
R6: `6 . 3 | . 2 .`

Let's solve this one.

Step 1: Column 1
Values: 4, 5, ?, ?, 1, 6.
Missing: 2, 3.
Cells: R3C1, R4C1.
* Check Row 3: `. 4 . | 1 . 2`. Missing 3,5,6.
* Check Row 4: `. 1 . | 3 . 6`. Missing 2,4,5.
* R3C1 must be 2 or 3. Row 3 needs 3,5,6. Intersection: 3.
* So R3C1 = 3.
* Therefore, R4C1 = 2.

Col 1 is: `4, 5, 3, 2, 1, 6`.

Step 2: Column 2
Values: ?, ?, 4, 1, ?, ?.
Given: R3C2=4, R4C2=1.
Missing: 2, 3, 5, 6.
Cells: R1C2, R2C2, R5C2, R6C2.
* R1: `4 . 2 | . 1 .`. Missing 3,5,6.
* R2: `5 . 1 | . 3 .`. Missing 2,4,6.
* R5: `1 . 4 | . 6 .`. Missing 2,3,5.
* R6: `6 . 3 | . 2 .`. Missing 1,4,5.

Let's look at Region 1 (Top Left, R1-2, C1-3).
Cells:
R1: 4, ?, 2
R2: 5, ?, 1
Present: 1, 2, 4, 5.
Missing: 3, 6.
Cells: R1C2, R2C2.
* R1C2 and R2C2 are 3 and 6.
* Check Col 2.

Let's look at Region 3 (Mid Left, R3-4, C1-3).
Cells:
R3: 3, 4, ?
R4: 2, 1, ?
Present: 1, 2, 3, 4.
Missing: 5, 6.
Cells: R3C3, R4C3.
* R3C3 and R4C3 are 5 and 6.

Let's look at Region 5 (Bot Left, R5-6, C1-3).
Cells:
R5: 1, ?, 4
R6: 6, ?, 3
Present: 1, 3, 4, 6.
Missing: 2, 5.
Cells: R5C2, R6C2.
* R5C2 and R6C2 are 2 and 5.

Now back to Col 2.
Cells:
R1C2: 3 or 6.
R2C2: 6 or 3.
R3C2: 4.
R4C2: 1.
R5C2: 2 or 5.
R6C2: 5 or 2.

Let's determine R1C2/R2C2.
Look at Row 1: `4, R1C2, 2, ..., 1, ...`.
Look at Row 2: `5, R2C2, 1, ..., 3, ...`.

Let's look at Col 3.
Values: 2, 1, R3C3, R4C3, 4, 3.
Missing: 5, 6.
R3C3, R4C3 are 5, 6.
* Check Row 3: `3, 4, R3C3, 1, R3C5, 2`. Missing 5, 6.
* Check Row 4: `2, 1, R4C3, 3, R4C5, 6`. Missing 4, 5.
* R4C3 must be 5 or 6. But Row 4 missing is 4,5. So R4C3 MUST be 5.
* Therefore, R3C3 = 6.

So Col 3 is: `2, 1, 6, 5, 4, 3`.

Now Row 4: `2, 1, 5, 3, R4C5, 6`.
Missing: 4.
So R4C5 = 4.

Now Row 3: `3, 4, 6, 1, R3C5, 2`.
Missing: 5.
So R3C5 = 5.

Now Col 5.
Values: R1C5=1, R2C5=3, R3C5=5, R4C5=4, R5C5=6, R6C5=2.
Col 5 is complete: `1, 3, 5, 4, 6, 2`.

Now Region 2 (Top Right, R1-2, C4-6).
Cells:
R1: R1C4, 1, R1C6
R2: R2C4, 3, R2C6
Present in Region: 1, 3.
Missing: 2, 4, 5, 6.

Look at Row 1: `4, R1C2, 2, R1C4, 1, R1C6`.
Missing: 3, 5, 6.
R1C2 is 3 or 6.
So R1C4, R1C6 are from {5, 6} or {3, 5}?
If R1C2=3, R1 missing 5,6.
If R1C2=6, R1 missing 3,5.

Look at Row 2: `5, R2C2, 1, R2C4, 3, R2C6`.
Missing: 2, 4, 6.
R2C2 is 6 or 3.

Let's use Col 4.
Values: R1C4, R2C4, 1, 3, R5C4, R6C4.
Missing: 2, 4, 5, 6.
Present: 1, 3.

Let's use Col 6.
Values: R1C6, R2C6, 2, 6, R5C6, R6C6.
Present: 2, 6.
Missing: 1, 3, 4, 5.

Let's go back to R1C2 / R2C2.
We know R5C2/R6C2 are 2/5.
Col 2 missing: 2,3,5,6.
R1C2, R2C2 are 3,6.
R5C2, R6C2 are 2,5.

Look at Row 5: `1, R5C2, 4, R5C4, 6, R5C6`.
Missing: 2, 3, 5.
R5C2 is 2 or 5.

Look at Row 6: `6, R6C2, 3, R6C4, 2, R6C6`.
Missing: 1, 4, 5.
R6C2 is 5 or 2. But Row 6 missing doesn't include 2.
Wait, Row 6 has `6, 3, 2`.
Missing 1, 4, 5.
So R6C2 MUST be 5.
Therefore, R5C2 = 2.

Now Col 2:
R5C2=2, R6C2=5.
Remaining for Col 2: R1C2, R2C2 are 3, 6.

Look at Row 1: `4, R1C2, 2, ...`.
If R1C2=3, Row 1 missing 5,6.
If R1C2=6, Row 1 missing 3,5.

Look at Row 2: `5, R2C2, 1, ...`.
If R2C2=6, Row 2 missing 2,4.
If R2C2=3, Row 2 missing 2,4,6? No, 3 is used.

Let's look at Col 4.
R3C4=1, R4C4=3.
R1C4, R2C4, R5C4, R6C4.

Look at Region 4 (Mid Right, R3-4, C4-6).
Cells:
R3: 1, 5, 2
R4: 3, 4, 6
Region 4 is complete: `1,5,2 / 3,4,6`.

Look at Region 6 (Bot Right, R5-6, C4-6).
Cells:
R5: R5C4, 6, R5C6
R6: R6C4, 2, R6C6
Present: 2, 6.
Missing: 1, 3, 4, 5.

Row 5 Missing: 3, 5. (Since R5C2=2, R5 is `1,2,4,?,6,?`. Missing 3,5).
So R5C4, R5C6 are 3, 5.

Row 6 Missing: 1, 4. (Since R6C2=5, R6 is `6,5,3,?,2,?`. Missing 1,4).
So R6C4, R6C6 are 1, 4.

Check Col 4:
R5C4 is 3 or 5.
R6C4 is 1 or 4.
R1C4, R2C4.
Col 4 Present: 1 (R3), 3 (R4).
Missing: 2, 4, 5, 6.
R6C4 is 1 or 4. But Col 4 has 1. So R6C4 cannot be 1.
Therefore, R6C4 = 4.
Therefore, R6C6 = 1.

Now Row 6 is: `6, 5,