#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,n-1,0)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 100000000

typedef long long ll;

int main() {
    int i, k;
    double ans = 0;
    default_random_engine e;
    uniform_int_distribution<int> u{1,6};
    cin >> k;
    rep (i,500000) {
        int x = 0;
        int cnt = 0;
        while (x != k) {
            x += u(e);
            if (x > k)
                x = 0;
            cnt++;
        }
        ans += cnt;
    }
    cout << ans / 500000 << endl;
    return 0;
}