#include <iostream>
using namespace std;

const int d[7] = {2, 2, -1, -1, 2, -1 -1};

int main()
{
    int x;
    cin >> x;
    int a = 0;
    int ans = 0;
    for(int i = 0; i < 1000; i++)
    {
        if(a == x)
        {
            cout << ans << endl;
            return 0;
        }
        a += d[i % 7];
        ans += abs(d[i % 7]);
    }
}