Count the Twins

Every two matching cards form a twin-pair — and a value appearing three times makes THREE different pairs (count the ways!). 🎴

You get the cards. Print the total number of matching pairs. Feel free to check every pair — or tally first and do pair-math.

Example:

Input: cards = [3, 5, 3, 5, 3] Output: 4

3 appears 3 times, making 3 × 2 ÷ 2 = 3 pairs; 5 appears 2 times, making 1 pair — 3 + 1 = 4 pairs total.