public static int surfaceArea(List<List<Integer>> A) {
    // Write your code here
        int front = 0;int side1 = 0;int side2 = 0;int bttm = 0;int back = 0;int top = 0;
        int frontInt = 0;int sideInt = 0;//Internals
        //Side1 and Side2
        side1 = A.get(0).stream().mapToInt(Integer::intValue).sum();
        side2 = A.get(A.size()-1).stream().mapToInt(Integer::intValue).sum();
        int i = 0;
        for(List<Integer> list : A){
            int zeroCount = (int) list.stream().filter(n -> n == 0).count();
            front += list.get(0);//Only works if no empty space..i.e filled with 0 
            top += (list.size()-zeroCount);//Those with 0 height
            bttm = top;
            back += list.get(list.size()-1);
            //Calculate front and side internals
            if(i>0){
                List<Integer> B = A.get(i-1);
                int maxLength = Math.max(list.size(), B.size());

        sideInt += IntStream.range(0, maxLength)
            .map(h -> {
                int a = h < list.size() ? list.get(h) : 0;
                int b = h < B.size() ? B.get(h) : 0;
                return Math.abs(a - b);
            })
            .sum();
            }
            frontInt += IntStream.range(1, list.size())
            .map(k -> Math.abs(list.get(k) - list.get(k - 1)))
            .sum();
            i++;
        }
        System.out.printf("front: %d,side1: %d,side2: %d,back: %d, top: %d, bttm: %d, sideInt: %d, frtInt: %d",front,side1,side2,back,top,bttm,sideInt,frontInt);
        return front+side1+side2+back+top+bttm+sideInt+frontInt;
    }