#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; ++i)
#define all(a) (a).begin(), (a).end()

int main() {
    cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    
    int k;
    cin >> k;

    if (k == 0) {
        double pi = 3.141592653589793238;
        double ans = pi*pi/6;
        cout << fixed << setprecision(20) << ans << '\n';
        return 0;
    }
    
    double ans = 0;
    rep(i, 1, k + 1) {
        ans += 1 / double(i);
    }
    
    ans /= (double)k;
    
    cout << fixed << setprecision(20) << ans << '\n';
}