#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define int ll
#define endl '\n'
#define pii pair<int , int>
#define _FastIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb emplace_back
#define pii pair<int , int>
#define F first
#define S second
#define M_PI 3.14159265358979323846
const int mod = 1000000007;
const int MAXX = 2e6 + 5;

int n , m;
int a[MAXX];
vector<int> v[MAXX];
int mp[MAXX];

signed main()
{
    _FastIO;
    cout.precision(12);
    cin >> n;
    long double ans = n;
    long double s = n * 1.00;
    for(int i = 3; i <= n; i++){
        long double p = s * 1.00 / ((i - 1) * 1.00) * 1.00;
        ans = ans * 1.00 + p * 1.00;
    }
    cout << fixed << ans << endl;
    return 0;
}

#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pint = pair<int,int>;


int main()
{
	int N; cin >> N;
	double ex = 0;
	for(int i = 1; i < N; i++) {
		ex += (double)N / i;
	}
	cout << fixed <<setprecision(12) << ex << endl; 
}