Unique Namespace Identifiers

You are designing a system to generate the shortest unique identifier for a list of usernames. For each username, find the shortest prefix that is NOT a prefix of any other username in the set. If a username is entirely a prefix of another (e.g., 'art' and 'artist'), the shorter one cannot be shortened further, so output the whole string. Example: Input: 3 apple apply dog Output: appl-e appl-y d (Note: In this specific problem format, for 'apple' and 'apply', 'appl' is shared, so 'apple' becomes 'apple' and 'apply' becomes 'apply' because the first unique char is the 5th one).