static ArrayList<Integer> merge_one_into_another(ArrayList<Integer> arr1, ArrayList<Integer> arr2) {
        int i = 0;
        int j = 0;
        while(i < arr1.size()) {
            if(arr1.get(i) <= arr2.get(j) || arr2.get(j) == 0) {
                for(int i1 = arr2.size()-1; i1 > j; i1--) {
                    arr2.set(i1, arr2.get(i1-1));
                }
                arr2.set(j, arr1.get(i));
                i++;
                j++;
            } else {
                 j++;
            }
        }

        return arr2;
    }