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

You are given an integer array rolls of length n and an integer k. You roll a k sided dice numbered from 1 to k, n times, where the result of the ith roll is rolls[i].
Return the length of the shortest sequence of rolls so that there's no such subsequence in rolls.
A sequence of rolls of length len is the result of rolling a k sided dice len times.
 
Please complete the following python code precisely:
```python
class Solution:
    def shortestSequence(self, rolls: List[int], k: int) -> int:
```