Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given an integer n, return true if n has exactly three positive divisors. Otherwise, return false.
An integer m is a divisor of n if there exists an integer k such that n = k * m.
 
Please complete the following python code precisely:
```python
class Solution:
    def isThree(self, n: int) -> bool:
```