public static int hourglassSum(List<List<Integer>> arr) {
        int max = Integer.MIN_VALUE;
        
        for (int row = 0; row < 4; row++) {
            for (int col = 0; col < 4; col++ ) {
                int sum = arr.get(row).get(col) + arr.get(row).get(col + 1) + arr.get(row).get(col + 2) + arr.get(row + 1).get(col + 1) + arr.get(row + 2).get(col) + arr.get(row + 2).get(col + 1) + arr.get(row + 2).get(col + 2);
                
                if (sum > max) {
                    max = sum;
                }
            }
        }
        
        return max;
    }