import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt();
            if(n != 0){//若n = 0,表示输入结束
                System.out.println(Num(n));
            }
        }
    }
    public static int Num(int n){
        int sum = 0;
        while(n >= 3){
            int m = n % 3;
            sum += n / 3;
            n = n / 3 + m;
        }
        if(n == 2){
            sum++;
        }
       return sum;
    }
}