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

Given two integer arrays nums1 and nums2 of length n, count the pairs of indices (i, j) such that i < j and nums1[i] + nums1[j] > nums2[i] + nums2[j].
Return the number of pairs satisfying the condition.
 
Please complete the following python code precisely:
```python
class Solution:
    def countPairs(self, nums1: List[int], nums2: List[int]) -> int:
```