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
* */
}