#include<iostream>
using namespace std;


int main() {
    int n = 0;
    while (cin >> n) {
        int sum = 0;
        while (n > 1) {
            int temp = n / 3;
            int num = n % 3;
            n = temp + num;
            sum += temp;
            if (n == 2) {
                sum++;
                break;
            }
        }
        if (n == 0) {
            continue;
        }
        cout << sum << endl;
    }
    return 0;
}