The Lonely Number

Every dance move was performed twice — except one, done only once. Find the loner. 🕺

You get the nums where every value appears exactly twice except one value appearing once. Print the lonely value.

Example:

Input: nums = [7, 3, 7, 9, 3] Output: 9

Tallying gives 7→2, 3→2, 9→1 — only 9 appears exactly once.