Categorize the following passage into one of the five stages of the customer journey.
A customer is writing a review of a product they recently purchased.
Stage 4: Retention.
Complete the following task based on the instruction and optional input provided.### Instruction:
Categorize the following passage into one of the five stages of the customer journey.

### Input:
A customer is writing a review of a product they recently purchased.

### Output:
Stage 4: Retention.