原题链接https://leetcode.com/problems/excel-sheet-column-title/

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

1 -> A
2 -> B
3 -> C
...
26 -> Z
27 -> AA
28 -> AB 
...

Example 1:

Input: 1
Output: "A"
Example 2:

Input: 28
Output: "AB"
Example 3:

Input: 701
Output: "ZY"

class Solution:
    def convertToTitle(self, n: int) -> str:
        num_to_letter = "0ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        if not isinstance(n, int):
            return -1
        
        res =""
        
        while n:
            n, left = divmod(n-1, 26)
            res = num_to_letter[left+1] + res
            
        return res