You are given a license key represented as a string s that consists of only alphanumeric characters and dashes. The string is separated into n + 1 groups by n dashes. You are also given an integer k.
We want to reformat the string s such that each group contains exactly k characters, except for the first group, which could be shorter than k but still must contain at least one character. Furthermore, there must be a dash inserted between two groups, and you should convert all lowercase letters to uppercase.
Return the reformatted license key.
Input: s = "5F3Z-2e-9-w", k = 4
Explanation: The string s has been split into two parts, each part has 4 characters.
Note that the two extra dashes are not needed and can be removed.
Input: s = "2-5g-3-J", k = 2
Explanation: The string s has been split into three parts, each part has 2 characters except the first part as it could be shorter as mentioned above.
1 <= s.length <= 10^5
s consists of English letters, digits, and dashes ‘-‘.