Last Stone Weight

You have a pile of stones with positive integer weights. Each turn, pick the two heaviest stones, x <= y, and smash them:

• if x == y, both are destroyed
• otherwise x is destroyed and y becomes y - x

Repeat until at most one stone is left. Return its weight, or 0 if none remain.

Example 1

Input: stones = [2,7,4,1,8,1]
Output: 1

8 and 7 → 1; 4 and 2 → 2; 2 and 1 → 1; 1 and 1 → gone; one stone of weight 1 is left.

Example 2

Input: stones = [1]
Output: 1

Example 3

Input: stones = [3,7,2]
Output: 2

7 and 3 → 4; 4 and 2 → 2.

Constraints

• 1 <= len(stones) <= 3 * 10^4
• 1 <= stones[i] <= 1000