/* #region Head */

// #include <bits/stdc++.h>
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert> // assert.h
#include <cmath>   // math.h
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U> using um = unordered_map<T, U>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqa = priority_queue<T, vc<T>, greater<T>>;
template <class T> using us = unordered_set<T>;

#define TREP(T, i, m, n) for (T i = (m), i##_len = (T)(n); i < i##_len; ++(i))
#define TREPM(T, i, m, n) for (T i = (m), i##_max = (T)(n); i <= i##_max; ++(i))
#define TREPR(T, i, m, n) for (T i = (m), i##_min = (T)(n); i >= i##_min; --(i))
#define TREPD(T, i, m, n, d) for (T i = (m), i##_len = (T)(n); i < i##_len; i += (d))
#define TREPMD(T, i, m, n, d) for (T i = (m), i##_max = (T)(n); i <= i##_max; i += (d))

#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define REPIR(itr, ds) for (auto itr = ds.rbegin(); itr != ds.rend(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define ISIZE(x) ((int)(x).size())
#define PERM(c)                                                                                                        \
    sort(ALL(c));                                                                                                      \
    for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());
#define CEIL(a, b) (((a) + (b)-1) / (b))

#define endl '\n'

constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr int IINF = 1'000'000'007LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;

// 前方宣言
template <typename T> istream &operator>>(istream &is, vc<T> &vec);
template <typename T> ostream &operator<<(ostream &os, const vc<T> &vec);
template <typename T> ostream &operator>>(ostream &os, const vc<T> &vec);
template <typename T, size_t _Nm> istream &operator>>(istream &is, array<T, _Nm> &arr);
template <typename T, size_t _Nm> ostream &operator<<(ostream &os, const array<T, _Nm> &arr);
template <typename T, size_t _Nm> ostream &operator>>(ostream &os, const array<T, _Nm> &arr);
template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var);
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &pair_var);
template <class T> ostream &out_iter(ostream &os, const T &map_var);
template <typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &map_var);
template <typename T, typename U> ostream &operator<<(ostream &os, const um<T, U> &map_var);
template <typename T> ostream &operator<<(ostream &os, const set<T> &set_var);
template <typename T> ostream &operator<<(ostream &os, const us<T> &set_var);
template <typename T> ostream &operator<<(ostream &os, const pq<T> &pq_var);
template <typename T> ostream &operator<<(ostream &os, const queue<T> &queue_var);
template <typename T> ostream &operator<<(ostream &os, const stack<T> &stk_var);

template <typename T> istream &operator>>(istream &is, vc<T> &vec) { // vector 入力
    for (T &x : vec)
        is >> x;
    return is;
}
template <typename T> ostream &operator<<(ostream &os, const vc<T> &vec) { // vector 出力 (for dump)
    os << "{";
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "" : ", ");
    os << "}";
    return os;
}
template <typename T> ostream &operator>>(ostream &os, const vc<T> &vec) { // vector 出力 (inline)
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "\n" : " ");
    return os;
}

template <typename T, size_t _Nm> istream &operator>>(istream &is, array<T, _Nm> &arr) { // array 入力
    REP(i, 0, SIZE(arr)) is >> arr[i];
    return is;
}
template <typename T, size_t _Nm> ostream &operator<<(ostream &os, const array<T, _Nm> &arr) { // array 出力 (for dump)
    os << "{";
    REP(i, 0, SIZE(arr)) os << arr[i] << (i == i_len - 1 ? "" : ", ");
    os << "}";
    return os;
}

template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var) { // pair 入力
    is >> pair_var.first >> pair_var.second;
    return is;
}
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &pair_var) { // pair 出力
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

// map, um, set, us 出力
template <class T> ostream &out_iter(ostream &os, const T &map_var) {
    os << "{";
    REPI(itr, map_var) {
        os << *itr;
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    return os << "}";
}
template <typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &map_var) {
    return out_iter(os, map_var);
}
template <typename T, typename U> ostream &operator<<(ostream &os, const um<T, U> &map_var) {
    os << "{";
    REPI(itr, map_var) {
        auto [key, value] = *itr;
        os << "(" << key << ", " << value << ")";
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    os << "}";
    return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, const us<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, const pq<T> &pq_var) {
    pq<T> pq_cp(pq_var);
    os << "{";
    if (!pq_cp.empty()) {
        os << pq_cp.top(), pq_cp.pop();
        while (!pq_cp.empty())
            os << ", " << pq_cp.top(), pq_cp.pop();
    }
    return os << "}";
}

// tuple 出力
template <size_t N = 0, bool end_line = false, typename... Args> ostream &operator<<(ostream &os, tuple<Args...> &a) {
    if constexpr (N < std::tuple_size_v<tuple<Args...>>) {
        os << get<N>(a);
        if constexpr (N + 1 < std::tuple_size_v<tuple<Args...>>) {
            os << ' ';
        } else if constexpr (end_line) {
            os << '\n';
        }
        return operator<< <N + 1, end_line>(os, a);
    }
    return os;
}
template <typename... Args> void print_tuple(tuple<Args...> &a) { operator<< <0, true>(std::cout, a); }

void pprint() { std::cout << endl; }
template <class Head, class... Tail> void pprint(Head &&head, Tail &&...tail) {
    std::cout << head;
    if (sizeof...(Tail) > 0) std::cout << ' ';
    pprint(move(tail)...);
}

// dump
#define DUMPOUT cerr
void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head &&head, Tail &&...tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(move(tail)...);
}

// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmax(T &xmax, const U &x, Comp comp = {}) {
    if (comp(xmax, x)) {
        xmax = x;
        return true;
    }
    return false;
}

// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmin(T &xmin, const U &x, Comp comp = {}) {
    if (comp(x, xmin)) {
        xmin = x;
        return true;
    }
    return false;
}

// ローカル用
#ifndef ONLINE_JUDGE
#define DEBUG_
#endif

#ifndef MYLOCAL
#undef DEBUG_
#endif

#ifdef DEBUG_
#define DEB
#define dump(...)                                                                                                      \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                                                                    \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl                                        \
            << "    ",                                                                                                 \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

#define VAR(type, ...)                                                                                                 \
    type __VA_ARGS__;                                                                                                  \
    assert((std::cin >> __VA_ARGS__));

template <typename T> istream &operator,(istream &is, T &rhs) { return is >> rhs; }
template <typename T> ostream &operator,(ostream &os, const T &rhs) { return os << ' ' << rhs; }

struct AtCoderInitialize {
    static constexpr int IOS_PREC = 15;
    static constexpr bool AUTOFLUSH = false;
    AtCoderInitialize() {
        ios_base::sync_with_stdio(false), std::cin.tie(nullptr), std::cout.tie(nullptr);
        std::cout << fixed << setprecision(IOS_PREC);
        if (AUTOFLUSH) std::cout << unitbuf;
    }
} ATCODER_INITIALIZE;

void Yn(bool p) { std::cout << (p ? "Yes" : "No") << endl; }
void YN(bool p) { std::cout << (p ? "YES" : "NO") << endl; }

template <typename T> constexpr void operator--(vc<T> &v, int) noexcept {
    for (int i = 0; i < ISIZE(v); ++i)
        v[i]--;
}
template <typename T> constexpr void operator++(vc<T> &v, int) noexcept {
    for (int i = 0; i < ISIZE(v); ++i)
        v[i]++;
}

/* #endregion */

// #include <atcoder/all>
// using namespace atcoder;

struct Eratosthenes {
    int n;
    vc<int> is_prime;
    vc<int> min_factor;
    vc<int> mobius; // mobius[i] := メビウス関数 μ(i)

    Eratosthenes(const int n) : n(n), is_prime(n + 1, true), min_factor(n + 1, -1), mobius(n + 1, 1) {
        is_prime[0] = false;
        is_prime[1] = false;
        min_factor[1] = 1;

        TREPM(int, p, 2, n) {
            if (not is_prime[p]) {
                continue;
            }
            min_factor[p] = p;
            mobius[p] = -1;

            int q = p * 2;
            while (q <= n) {
                is_prime[q] = false;
                if (min_factor[q] == -1) {
                    min_factor[q] = p;
                }
                if ((q / p) % p == 0) {
                    mobius[q] = 0;
                } else {
                    mobius[q] = -mobius[q];
                }
                q += p;
            }
        }
    }

    // n 以下の素数一覧を返す
    vc<int> primes() const {
        vc<int> ret;
        REPM(i, 2, n) if (is_prime[i]) ret.push_back(i);
        return ret;
    }

    // N の素因数分解
    vc<pair<int, int>> factorize(const int N) const {
        vc<pair<int, int>> ret;
        int n = N;
        while (n > 1) {
            const int p = min_factor[n];
            int exp = 0;

            while (min_factor[n] == p) {
                n /= p;
                exp += 1;
            }
            ret.emplace_back(p, exp);
        }
        return ret;
    }

    // N の約数
    vc<int> divisors(const int N) const {
        vc<int> ret = {1};
        vc<pair<int, int>> pf = factorize(N);
        for (const auto &[p, exp] : pf) {
            const int m = ISIZE(ret);
            TREP(int, i, 0, m) {
                int v = 1;
                TREP(int, j, 0, exp) {
                    v *= p;
                    ret.push_back(ret[i] * v);
                }
            }
        }
        sort(ALL(ret));
        return ret;
    }
};

// Problem
void solve() {
    VAR(ll, n); //

    Eratosthenes s(n + 1);

    // dp[i] := iが1になるまでの回数の期待値
    vc<ld> dp(n + 1, -1);
    dp[1] = 0;
    REP(i, 2, n + 1) {
        // 1以上i未満へ遷移した場合の期待値を求める
        const vc<int> divisors = s.divisors(i);
        // dump(i, divisors);
        ld dsum = 0.0l;
        for (const int &d : divisors) {
            // if (d == i) continue;
            dsum += dp[d] + 1.0l;
        }
        // dump(dsum, i - 1, SIZE(divisors));
        // dsum/SIZE(divisors) 回: SIZE(divisors) 個
        // 1 回: (i-1) - SIZE(divisors) 個
        dp[i] = (1.0l + dsum + i - 1 - (SIZE(divisors) - 1)) / (i - 1);
    }
    // dump(dp);
    pprint(dp.back());
}

// entry point
int main() {
    solve();
    return 0;
}