#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
// #include <atcoder/modint>
// #include <atcoder/fenwicktree>
// #include <atcoder/segtree>
// #include <atcoder/scc>

#define all(x) begin(x), end(x)

using namespace std;
// using namespace atcoder;
// using mint = modint998244353;
// using mint = modint1000000007;
using i32 = int;
using i64 = long long;
using ld = long double;

void debug(vector<int> a) {
    for (auto x : a) cout << x << ' ';
    cout << endl;
}

void debug(vector<vector<int>> a) {
    for (auto y : a) debug(y);
}

template <typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b and (a = b, true);}

template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b and (a = b, true);}

const i64 supl = LONG_LONG_MAX - 100;

void main_() {
    i32 k; cin >> k;
    vector<ld> dpa(k + 6), dpb(k + 6);
    for (int i = k + 1 ; i < k + 6 ; i++) dpa[i] = 1;

    for (int i = k - 1 ; i >= 0 ; i--) {
        for (int j = 1 ; j <= 6 ; j++) {
            dpa[i] += 1.0l/6.0l * dpa[i + j];
            dpb[i] += 1.0l/6.0l * dpb[i + j];
        }
        dpb[i] += 1.0l;
    }

    cout << fixed << setprecision(3);
    // cout << dpa[0] << ' ' << dpb[0] << endl;
    cout << dpb[0] * 1.0l/(1.0l - dpa[0]) << endl;
}

int main() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    main_();

    return 0;
}