for i in range(num_tags): # Replace None in this line with the proper range.

```
# Initialize best_probs at POS tag 'i', column 0
# Check the formula in the instructions above
best_probs[i,0] = best_probs[i,0] = math.log(A[s_idx,i]) + math.log(B[i,vocab[corpus[0]]] )
```

Hi @Arin_Jain

The error tells that your code is probably taking a `log`

of a number that is less than or equal to zero.

So make sure that the matrix `A`

is greater than zero - make sure that the outputs after UNQ_C3 matches the expected outputs:

```
Expected Output
A at row 0, col 0: 0.000007040
A at row 3, col 1: 0.1691
View a subset of transition matrix A
RBS RP SYM TO UH
RBS 2.217069e-06 2.217069e-06 2.217069e-06 0.008870 2.217069e-06
RP 3.756509e-07 7.516775e-04 3.756509e-07 0.051089 3.756509e-07
SYM 1.722772e-05 1.722772e-05 1.722772e-05 0.000017 1.722772e-05
TO 4.477336e-05 4.472863e-08 4.472863e-08 0.000090 4.477336e-05
UH 1.030439e-05 1.030439e-05 1.030439e-05 0.061837 3.092348e-02
```

Cheers