#include <bits/stdc++.h>
using namespace std;

int x, i, j, m;

int main()
{
	cin >> x;

	while (i != x) {
		int u = j % 7;

		if (u == 0 || u == 1 || u == 4) {
			i += 2;
			m += 2;
		}
		else {
			i--;
			m++;
		}

		j++;
	}

	cout << m << endl;
}