#include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <math.h> // sqrt
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <unordered_set> // unordered_set
#include <iomanip> // setprecision
using namespace std;
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vb = vector<bool>;
using vll = vector<long long>;
using pii = pair<int, int>;
using psi = pair<string, int>;

int main() {
    ll x;
    cin >> x;
    ll ans = floor(x / 11) * 2, a = x % 11;
    if (a > 6) {
        ans += 2;
    }
    else if (a > 0) {
        ans++;
    }
    cout << ans << endl;
}

#include <stdio.h>
#include <math.h>

using namespace std;
typedef long long llong;

#define MAX
const llong mod = 1000000000 + 7;

int main()
{
  double R;
  scanf("%lf", &R);

  printf("%lf", 2.0 * M_PI * R);

  return 0;
}