#include <bits/stdc++.h>
#define all(x) begin(x),end(x)
#define rall(x) (x).rbegin(),(x).rend()
#define REP(i,b,n) for(int i=(int)(b);i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define repsz(i,v) rep(i,(v).size())
#define aur auto&
#define bit(n) (1LL<<(n))
#define eb emplace_back
#define mt make_tuple
#define fst first
#define snd second
using namespace std;
typedef long long ll;
//#define int long long
template<class C>int size(const C &c){ return c.size(); }
template<class T>bool chmin(T&a,const T&b){if(a<=b)return false;a=b;return true;}
template<class T>bool chmax(T&a,const T&b){if(a>=b)return false;a=b;return true;}

bool solve(){
    int k; cin >> k;
    using R = long double;
    vector<R> prob(k+6);
    prob[0] = 1;
    rep(i, k) REP(j, 1, 7) prob[i+j] += prob[i] / 6.;

    vector<R> expect(k+6);
    expect[0] = 0;
    rep(i, k+6) if(i){
        R sum = 0;
        for(int j = max(0, i-6); j < min(i, k); ++j) sum += prob[j];
        for(int j = max(0, i-6); j < min(i, k); ++j) expect[i] += (prob[j] / sum) * (expect[j] + 1);
    }
    R ans = expect[k];
    R num = 1 / prob[k] - 1;
    R sum = 1 - prob[k];
    for(int i = k+1; i < k+6; ++i) ans += num * (prob[i] / sum) * expect[i];
    cout << ans << endl;
    return true;
}
signed main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << std::fixed << std::setprecision(10);
    solve();
    return 0;
}
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