#include<iostream>

using namespace std;

int CountVial(int n)
{
    int m = 0;
    while (n > 1)
    {
        int s = n / 3;
        int l = n % 3;
        m += s;
        n = l + s;
        if (n == 2)
        {
            m++;
            break;
        }
    }
    return m;
}

int main()
{
    int n, sum;
    while (cin >> n)
    {
        if (n == 0)
        {
            break;
        }
        sum = CountVial(n);
        cout << sum << endl;
    }
    return 0;
}