[leetcode]License Key Formatting

class Solution:
    def licenseKeyFormatting(self, S: str, K: int) -> str:
        lst = []
        for c in S:
            if c == ‘-‘:
                continue
            if c >= ‘a‘ and c <= ‘z‘:
                c = chr(ord(c) - ord(‘a‘) + ord(‘A‘))
            lst.append(c)
        ret = ‘‘
        for i in range(len(lst)):
            ret += lst[i]
            rem = len(lst) % K - 1
            if rem < 0:
                rem += K
            if i != len(lst) - 1 and i % K == rem:
                ret += ‘-‘
        return ret