The Missing Rank

Ranks 1 through n were handed out, one kid went home early, and the pile is shuffled. 🏠

You get the shuffled ranks with exactly one rank missing. Sort them and find the gap. Print the missing rank. (Careful — the missing one might be the very last!)

Example:

Input: ranks = [4, 1, 2, 5] Output: 3

Sorted, the list becomes [1, 2, 4, 5] — position 2 should hold 3 but holds 4 instead, revealing the gap.