public static long largestRectangle(List<int> h)
    {
        int highScore = 0;
        List<Tuple<int, int>> items = new List<Tuple<int, int>>();
        
        for(int i = 0; i < h.Count; i++)
        {
            int start = i;
            while(items.Count > 0 && items[items.Count - 1].Item2 > h[i])
            {
                Tuple<int, int> topOfStack = items[items.Count - 1];
                items.RemoveAt(items.Count - 1);
                highScore = Math.Max(highScore, topOfStack.Item2 * (i - topOfStack.Item1));
                start = topOfStack.Item1;
            }
            items.Add(new Tuple<int, int>(start, h[i]));
        }
        
        foreach(Tuple<int, int> item in items)
        {
            highScore = Math.Max(highScore, item.Item2 * (h.Count - item.Item1));
        }
        
        return highScore;
    }