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

Given an array nums of integers and integer k, return the maximum sum such that there exists i < j with nums[i] + nums[j] = sum and sum < k. If no i, j exist satisfying this equation, return -1.
 
Please complete the following python code precisely:
```python
class Solution:
    def twoSumLessThanK(self, nums: List[int], k: int) -> int:
```