class HelloWorld {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        List<Integer> list = new ArrayList<>();
        while (in.hasNext()) {
            int i = in.nextInt();
            if (i==0) {
                break;
            }
            int j =i/3;
            int y =i%3;
            int s = 0;
            int all = j;
            while (j!=0) {

                 s = j+y;
                j=s/3;
                y=s%3;
                all +=j;
            }

            if (y==2) {//剩余2个空瓶子换一个
                all+=1;
            }
            list.add(all);

        }
        for (Integer i :
                list) {
            System.out.println(i);
        }
    }
  /*
        * i = 40
        * 40/3 = 13...1
        * 13+1=14
        * 14/3 = 4...2
        * 4+2=6
        * 6/3=2...0
        * 2+0 = 2
        * 2/3=0...2
        * 30
        * 30/3 = 10...0
        * 10+0 = 10
        * 10/3 =3...1
        * 3+1=4
        * 4/3=1...1
        * 1+1=2
        * 2/3=0...2
        * 2
        * */
}