Given an array of integers heights representing the histogram's bar heights where the width of each bar is 1, return the area of the largest rectangle in the histogram.

Example 1:

Input: 2 1 5 6 2 3
Output: 10
Explanation: The largest rectangle has area 10 (bars at index 2-3, height 5, width 2).

Example 2:

Input: 2 4
Output: 4

Constraints:

• 1 ≤ heights.length ≤ 10⁵
• 0 ≤ heights[i] ≤ 10⁴

Input format: A single line of space-separated integers.

Output format: A single integer.