// template {{{ #include using namespace std; // #define int long long #define GET_MACRO(a, b, c, d, NAME, ...) NAME #define REP2(i, n) REP3(i, 0, n) #define REP3(i, a, b) REP4(i, a, b, 1) #define REP4(i, a, b, s) for (ll i = (a); i < (ll)(b); i += s) #define RREP2(i, n) RREP3(i, 0, n) #define RREP3(i, a, b) for (ll i = (b) - 1; i >= (ll)(a); i--) #define rep(...) GET_MACRO(__VA_ARGS__, REP4, REP3, REP2)(__VA_ARGS__) #define rrep(...) GET_MACRO(__VA_ARGS__,, RREP3, RREP2)(__VA_ARGS__) #define eb emplace_back #define ef emplace_front #define pb pop_back #define pf pop_front #define all(c) begin(c), end(c) #define mp make_pair #define mt make_tuple #define fi first #define se second #define popcnt __builtin_popcountll using uint = unsigned; using ll = long long; using ull = unsigned long long; using ld = long double; using vi = vector; using vvi = vector; template using maxheap = priority_queue, less>; template using minheap = priority_queue, greater>; const int INF = 1e9 + 10; const ll LLINF = 1e18 + 10; const int dx[] = {-1, 0, 1, 0}; const int dy[] = {0, -1, 0, 1}; const int dx8[] = {-1, -1, 0, 1, 1, 1, 0, -1}; const int dy8[] = {0, -1, -1, -1, 0, 1, 1, 1}; template inline T sq(T x){ return x * x; } template inline bool chmax(T &x, U y){ if (x >= y) return false; x = y; return true; } template inline bool chmin(T &x, U y){ if (x <= y) return false; x = y; return true; } template inline T& sort(T &c){ sort(all(c)); return c; } template inline T& reverse(T &c){ reverse(all(c)); return c; } template inline T& unique(T &c){ sort(all(c)); c.erase(unique(all(c)), end(c)); return c; } template inline T sorted(const T &c){ T d = c; return sort(d); } template inline T reversed(const T &c){ T d = c; return reverse(d); } template inline T uniqued(const T &c){ T d = c; return unique(d); } template T power(T x, long long r, const T &e = 1){ T res(e); while (r){ if (r & 1) res = res * x; x = x * x; r >>= 1; } return res; } // }}} int k; double e[20]; double calc(int x){ if (x >= k) return 0; if (e[x] > -1) return e[x]; double r = 1; rep(i, 1, 7) r += calc(x + i) / 6; return e[x] = r; } int main() { cin >> k; fill_n(e, 20, -1); printf("%.20f\n", calc(0)); }