Card War Line

Everyone holds one numbered card. The front TWO battle: the higher card wins, the winner rejoins the back, the loser is out. ⚔️

You get the cards (all different, front first). Battles continue until one card remains. Print it.

Example:

Input: cards = [3, 7, 1, 9, 4] Output: 9

3 vs 7 → 7 wins and rejoins the back. 1 vs 9 → 9 wins and rejoins. The winners keep battling until only the biggest card, 9, remains.