The conversation between human and AI assistant.
[|Human|] Rewrite the following algorithm using pseudocode.
[|AI|] ```
ALGORITHM simpleSum(n)
// calculates the sum of the first n natural numbers

DECLARE sum: INTEGER
DECLARE number: INTEGER

SET sum TO 0
SET number TO 0

WHILE number < n DO
    sum = sum + number
    number = number + 1
END WHILE

RETURN sum
```
[|Human|] 
Rewrite the following algorithm using pseudocode.