#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
//---------------------------------------------------------------------------------------------------
template <typename T> int gaussianElimination(vector<vector<T>> &A, int var = -1) {
    int N = A.size(), M = A[0].size();
    if (var < 0) {
        var = N;
        assert(N <= M);
    }
    int k = 0, rank = var;
    rep(i, 0, var) {
        int v = -1;
        for (int j = k; j < N && v == -1; j++) if (A[j][i] != 0) v = j;
        if (v == -1) {
            rank--;
            continue;
        }
        //a[i] = k;
        swap(A[k], A[v]);
        T x = T(1) / A[k][i];
        rep(j, 0, M) A[k][j] = A[k][j] * x;
        rep(j, 0, N) if(j != k) {
            T y = A[j][i];
            for (int h = M - 1; h >= i; h--) 
                A[j][h] = A[j][h] - A[k][h] * y;
        }
        k++;
    }

    return rank;
}
template <typename T> void print(vector<vector<T>> &A) {
    int N = A.size(), M = A[0].size();
    rep(y, 0, N) { rep(x, 0, M) cout << A[y][x] << "\t"; cout << endl; }cout << endl;}
template<int MOD> struct ModInt {
    static const int Mod = MOD; unsigned x; ModInt() : x(0) { }
    ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    int get() const { return (int)x; }
    ModInt &operator+=(ModInt that) { if ((x += that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(ModInt that) { if ((x += MOD - that.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(ModInt that) { x = (unsigned long long)x * that.x % MOD; return *this; }
    ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
    ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
    ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
    ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
    ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
    ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0;
        while (b) { long long t = a / b; a -= t * b; std::swap(a, b); u -= t * v; std::swap(u, v); }
        return ModInt(u); }
    bool operator==(ModInt that) const { return x == that.x; }
    bool operator!=(ModInt that) const { return x != that.x; }
    ModInt operator-() const { ModInt t; t.x = x == 0 ? 0 : Mod - x; return t; }
};
template<int MOD> ostream& operator<<(ostream& st, const ModInt<MOD> a) { st << a.get(); return st; };
template<int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
    ModInt<MOD> r = 1; while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; }
typedef ModInt<5> mint;
typedef ModInt<1000000007> mint2;
/*---------------------------------------------------------------------------------------------------
　　　　　　　　　　　 ∧＿∧  
　　　　　 ∧＿∧ 　（´<_｀ ）　 Welcome to My Coding Space!
　　　　 （ ´_ゝ`）　/　 ⌒i     
　　　　／　　　＼　 　  |　|     
　　　 /　　 /￣￣￣￣/　　|  
　 ＿_(__ﾆつ/　    ＿/ .| .|＿＿＿＿  
　 　　　＼/＿＿＿＿/　（u　⊃  
---------------------------------------------------------------------------------------------------*/







int K;
//---------------------------------------------------------------------------------------------------
void _main() {
    cin >> K;

    vector<vector<double>> A(K, vector<double>(K + 1, 0));

    rep(i, 0, K) {
        rep(j, 1, 7) {
            int next = (i + j > K) ? 0 : i + j;
            A[i][K] -= 1.0 / 6;
            if (i + j != K) A[i][next] += 1.0 / 6;
        }
        A[i][i] -= 1;
    }


    //print(A);
    gaussianElimination(A);
    //print(A);

    double ans = A[0][K];
    printf("%.10f\n", ans);
}