#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <sys/time.h>
#include <random>
using namespace std;

#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
typedef complex<double> comp;
typedef vector< vector<ld> > matrix;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};
const int inf = 1e9 + 9;
const ll mod = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1);

int K;

// if index size = 0, LU decomposition failed.
vector<int> LUdecomposition(matrix& A) {
    const int n = A.size();
    vector<int> index(n);
    for (int i = 0; i < n; i++) index[i] = i;
    for (int i = 0; i < n; i++) {
        int pivot = i;
        for (int j = i+1; j < n; j++)
            if (abs(A[j][i]) > abs(A[pivot][i])) pivot = j;
        swap(A[pivot], A[i]);
        swap(index[pivot], index[i]);

        // failed
        if (abs(A[i][i]) < eps) {
            index.clear();
            return index;
        }

        for (int j = i+1; j < n; j++) {
            A[j][i] /= A[i][i];
            for (int k = i+1; k < n; k++)
                A[j][k] -= A[i][k] * A[j][i];
        }
    }

    return index;
}

vector<ld> solve_simuleq(matrix A, vector<ld> b) {
    vector<int> index = LUdecomposition(A);
    if (index.size() == 0) return vector<ld>(0);
    int n = A.size();

    vector<ld> c(n), tmp(n), res(n);
    for (int i = 0; i < n; i++) {
        c[i] = b[index[i]];
        for (int j = 0; j < i; j++)
            c[i] -= A[i][j] * c[j];
    }
    for (int i = n-1; i >= 0; i--) {
        tmp[i] = c[i];
        for (int j = n-1; j > i; j--)
            tmp[i] -= A[i][j] * tmp[j];
        tmp[i] /= A[i][i];
    }
    for (int i = 0; i < n; i++)
        res[index[i]] = tmp[i];
    
    return res;
}

ld solve() {
    matrix A(K, vector<ld>(K, 0.0));
    vector<ld> b(K);
    for (int i = 0; i < K; i++) {
        A[i][i] = 1.0;
        for (int j = 1; j <= 6; j++) {
            int k = i + j;
            if (k < K) A[i][k] -= 1.0/6.0;
            else if (k > K) A[i][0] -= 1.0/6.0;
        }
    }
    
    for (int i = 0; i < K; i++)
        b[i] = 1.0;

    return (solve_simuleq(A, b))[0];
}

void input() {
    cin >> K;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);

    input();
    cout << solve() << endl;
}