### Tell us what’s happening:

I have no idea how to increment left_array_index by 1.

### Your code so far

```
def merge_sort(array):
middle_point = len(array) // 2
left_part = array[:middle_point]
right_part = array[middle_point:]
merge_sort(left_part)
merge_sort(right_part)
left_array_index = 0
right_array_index = 0
sorted_index = 0
while left_array_index < len(left_part) and right_array_index < len(right_part):
# User Editable Region
if left_part[left_array_index] < right_part[right_array_index]:
array[sorted_index] = left_part[left_array_index]
left_array_index(+1)
# User Editable Region
```

### Your browser information:

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### Challenge Information:

Learn Data Structures by Building the Merge Sort Algorithm - Step 14