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

You are given a string s of lowercase English letters and an integer array shifts of the same length.
Call the shift() of a letter, the next letter in the alphabet, (wrapping around so that 'z' becomes 'a').

For example, shift('a') = 'b', shift('t') = 'u', and shift('z') = 'a'.

Now for each shifts[i] = x, we want to shift the first i + 1 letters of s, x times.
Return the final string after all such shifts to s are applied.
 
Please complete the following python code precisely:
```python
class Solution:
    def shiftingLetters(self, s: str, shifts: List[int]) -> str:
```