#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
// using namespace atcoder;
#define rep2(i,m,n) for (int i = (m); i < (n); ++i)
#define rep(i,n) rep2(i,0,n)
#define debug(x) cout << x << endl;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> P;
template<typename T> struct V : vector<T> { using vector<T>::vector; };
V() -> V<int>;
V(size_t) -> V<int>;
template<typename T> V(size_t, T) -> V<T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
const int INF = 1<<30;
const ll LINF = 1LL<<61;
// const ll MOD = 1000000007;
// using mint = modint1000000007;
ld eps = 1e-12;

ld power(ld x, int k)
{
    ld res = 1;
    while(k)
    {
        if(k & 1) res = (res * x);
        k >>= 1;
        x = (x * x);
    }
    return res;
}

ld sum(ll n, ld r)
{
    return (ld)r / (ld)(1 - r) - (r - power(r, n+1)) / (1 - r);
}

int main()
{
    ll n;
    cin >> n;
    if(n == 2)
    {
        cout << 1000000 << endl;
        return 0;
    }
    ld ans = 0;
    for(ll i=2; i<101010; i++)
    {
        ld tmp =  sum(n-1, (ld)1 / (ld)i);
        ans += tmp;
    }
    ll res = (ans * 1e9) + eps;
    res /= 1000;
    cout << res << endl;
    
    return 0;
}