Step 0

Starting puzzle

1 2 3 4 5 6 7 8 9
A   1     3        
B 9           1   4
C 5         1   2  
D       4       6 3
E   5     1     9  
F 2 8       3      
G   6   1         9
H 3   7           6
I         6     4  

Step 1

The number 3 does not yet appear in row E. Due to other 3s on the grid, the only place it can go is cell E3.

1 2 3 4 5 6 7 8 9
A   1     3        
B 9           1   4
C 5         1   2  
D       4       6 3
E   5 3   1     9  
F 2 8       3      
G   6   1         9
H 3   7           6
I         6     4  

Step 2

The number 3 does not yet appear in column 4. Due to other 3s on the grid, the only place it can go is cell I4.

1 2 3 4 5 6 7 8 9
A   1     3        
B 9           1   4
C 5         1   2  
D       4       6 3
E   5 3   1     9  
F 2 8       3      
G   6   1         9
H 3   7           6
I       3 6     4  

Step 3

The number 1 is missing from row H and its only possible position is cell H8.

1 2 3 4 5 6 7 8 9
A   1     3        
B 9           1   4
C 5         1   2  
D       4       6 3
E   5 3   1     9  
F 2 8       3      
G   6   1         9
H 3   7         1 6
I       3 6     4  

Step 4

Because of the number 1 just placed, the only position in column 9 for another 1 is cell F9.

1 2 3 4 5 6 7 8 9
A   1     3        
B 9           1   4
C 5         1   2  
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1         9
H 3   7         1 6
I       3 6     4  

Step 5

In box A7-C9, each of the cells A8 and A9 and C9 can only take one of the numbers 5 or 7 or 8. These 3 cells will use up these 3 numbers between them. Therefore the numbers can be eliminated from A7, C7, B8 in box A7-C9. The remaining possibilities are marked with small numbers.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5         1 369 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1         9
H 3   7         1 6
I       3 6     4  

Step 6

Cell B8 can only contain the number 3 since all other possible numbers have been eliminated.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5         1 69 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1         9
H 3   7         1 6
I       3 6     4  

Step 7

Because of the number 3 just placed, the only position in row C for another 3 is cell C2.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5 3       1 69 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1         9
H 3   7         1 6
I       3 6     4  

Step 8

Because of the number 3 just placed, the only position in column 7 for another 3 is cell G7.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5 3       1 69 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1     3   9
H 3   7         1 6
I       3 6     4  

Step 9

The number 4 is missing from column 2 and its only possible position is cell H2.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5 3       1 69 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G   6   1     3   9
H 3 4 7         1 6
I       3 6     4  

Step 10

Cell G1 can only contain the number 8 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A   1     3   69 578 578
B 9           1 3 4
C 5 3       1 69 2 78
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I       3 6     4  

Step 11

The number 8 is missing from column 8 and its only possible position is cell A8.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 57
B 9           1 3 4
C 5 3       1 69 2 7
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I       3 6     4  

Step 12

The number 5 is missing from box A7-C9 and its only possible position is cell A9.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9           1 3 4
C 5 3       1 69 2 7
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I       3 6     4  

Step 13

The number 7 is missing from box A7-C9 and its only possible position is cell C9.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9           1 3 4
C 5 3       1 69 2 7
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I       3 6     4  

Step 14

Cell I1 can only contain the number 1 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9           1 3 4
C 5 3       1 69 2 7
D       4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1     3 6     4  

Step 15

Because of the number 1 just placed, the only position in column 3 for another 1 is cell D3.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9           1 3 4
C 5 3       1 69 2 7
D     1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1     3 6     4  

Step 16

Cell D1 can only contain the number 7 since all other numbers are somewhere in its row, column or box.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9           1 3 4
C 5 3       1 69 2 7
D 7   1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1     3 6     4  

Step 17

Because of the number 7 just placed, the only position in column 2 for another 7 is cell B2.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7   1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1     3 6     4  

Step 18

The number 2 is missing from column 2 and its only possible position is cell I2.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7   1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1 2   3 6     4  

Step 19

D2 is the last empty cell in column 2 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1 2   3 6     4  

Step 20

Because of the number 9 just placed, the only position in column 3 for another 9 is cell I3.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6   1     3   9
H 3 4 7         1 6
I 1 2 9 3 6     4  

Step 21

G3 is the last empty cell in box G1-I3 and the missing number is 5.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3     1
G 8 6 5 1     3   9
H 3 4 7         1 6
I 1 2 9 3 6     4  

Step 22

The number 5 is missing from column 8 and its only possible position is cell F8.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3   5 1
G 8 6 5 1     3   9
H 3 4 7         1 6
I 1 2 9 3 6     4  

Step 23

G8 is the last empty cell in column 8 and the missing number is 7.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6     4  

Step 24

Because of the number 7 just placed, the only position in row I for another 7 is cell I6.

1 2 3 4 5 6 7 8 9
A   1     3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 25

The number 7 does not yet appear in row A. Due to other 7s on the grid, the only place it can go is cell A4.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8       3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 26

Because of the number 7 just placed, the only position in column 5 for another 7 is cell F5.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1     9  
F 2 8     7 3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 27

Because of the number 7 just placed, the only position in row E for another 7 is cell E7.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1   7 9  
F 2 8     7 3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 28

The number 9 does not yet appear in row F. Due to other 9s on the grid, the only place it can go is cell F4.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1   7 9  
F 2 8   9 7 3   5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 29

The number 4 does not yet appear in column 7. Due to other 4s on the grid, the only place it can go is cell F7.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E   5 3   1   7 9  
F 2 8   9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 30

Because of the number 4 just placed, the only position in row E for another 4 is cell E1.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8   9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 31

F3 is the last empty cell in box D1-F3 and the missing number is 6.

1 2 3 4 5 6 7 8 9
A   1   7 3   69 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 32

A1 is the last empty cell in column 1 and the missing number is 6.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3       1 69 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 33

The number 6 does not yet appear in column 7. Due to other 6s on the grid, the only place it can go is cell C7.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3       1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 34

A7 is the last empty cell in box A7-C9 and the missing number is 9.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3       1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 35

Because of the number 9 just placed, the only position in row C for another 9 is cell C5.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3     9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7         1 6
I 1 2 9 3 6 7   4  

Step 36

Because of the number 9 just placed, the only position in column 6 for another 9 is cell H6.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3     9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 37

The number 4 is missing from row C and its only possible position is cell C3.

1 2 3 4 5 6 7 8 9
A 6 1   7 3   9 8 5
B 9 7         1 3 4
C 5 3 4   9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 38

Because of the number 4 just placed, the only position in row A for another 4 is cell A6.

1 2 3 4 5 6 7 8 9
A 6 1   7 3 4 9 8 5
B 9 7         1 3 4
C 5 3 4   9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1     3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 39

Because of the number 4 just placed, the only position in column 5 for another 4 is cell G5.

1 2 3 4 5 6 7 8 9
A 6 1   7 3 4 9 8 5
B 9 7         1 3 4
C 5 3 4   9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4   3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 40

A3 is the last empty cell in row A and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7         1 3 4
C 5 3 4   9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4   3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 41

B3 is the last empty cell in box A1-C3 and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4   9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4   3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 42

C4 is the last empty cell in row C and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4   3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 43

G6 is the last empty cell in row G and the missing number is 2.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9   1 6
I 1 2 9 3 6 7   4  

Step 44

Because of the number 2 just placed, the only position in row H for another 2 is cell H7.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9  
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 45

Because of the number 2 just placed, the only position in column 9 for another 2 is cell E9.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4       6 3
E 4 5 3   1   7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 46

Because of the number 2 just placed, the only position in row D for another 2 is cell D5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8       1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2     6 3
E 4 5 3   1   7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 47

Because of the number 2 just placed, the only position in column 4 for another 2 is cell B4.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2     6 3
E 4 5 3   1   7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 48

D7 is the last empty cell in box D7-F9 and the missing number is 8.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1   7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 49

Because of the number 8 just placed, the only position in row E for another 8 is cell E6.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7     9 2 1 6
I 1 2 9 3 6 7   4  

Step 50

Because of the number 8 just placed, the only position in column 5 for another 8 is cell H5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7   8 9 2 1 6
I 1 2 9 3 6 7   4  

Step 51

Because of the number 8 just placed, the only position in row I for another 8 is cell I9.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7   8 9 2 1 6
I 1 2 9 3 6 7   4 8

Step 52

H4 is the last empty cell in box G4-I6 and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7   4 8

Step 53

I7 is the last empty cell in row I and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2   8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7 5 4 8

Step 54

D6 is the last empty cell in row D and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2     1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2 5 8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7 5 4 8

Step 55

B5 is the last empty cell in column 5 and the missing number is 5.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2 5   1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2 5 8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7 5 4 8

Step 56

B6 is the last empty cell in box A4-C6 and the missing number is 6.

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2 5 6 1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2 5 8 6 3
E 4 5 3   1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7 5 4 8

Step 57

E4 is the last empty cell in column 4 and the missing number is 6.

Congratulations - the puzzle is solved!

1 2 3 4 5 6 7 8 9
A 6 1 2 7 3 4 9 8 5
B 9 7 8 2 5 6 1 3 4
C 5 3 4 8 9 1 6 2 7
D 7 9 1 4 2 5 8 6 3
E 4 5 3 6 1 8 7 9 2
F 2 8 6 9 7 3 4 5 1
G 8 6 5 1 4 2 3 7 9
H 3 4 7 5 8 9 2 1 6
I 1 2 9 3 6 7 5 4 8
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