Input: heights = [2,1,5,6,2,3]
Explanation: The largest rectangle is formed by the bars with heights 5 and 6, having a width of 2, resulting in an area of 5 * 2 = 10 or 6 * 2 = 12. Considering the area to be width * height, the rectangle starts at 5 and ends before 2 (index 4) . Maximum area with height 6 and width one.