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

int main()
{
    freopen("Bai3_10.inp", "r", stdin);
    freopen("Bai3_10.out", "w", stdout);
    int n;
    cin >> n;
    double res = 0;
    for (int i = 1; i <= n; i++)
        res += (double)1 / (2 * i);
    cout << fixed << setprecision(2) << res;
}

#include <bits/stdc++.h>
using namespace std;
signed main(){
	freopen("Bai3_10.inp","r",stdin);
	freopen("Bai3_10.out","w",stdout);
	double ans=0;
	int n;
	cin>>n;
	for(int i=2;i<=2*n;i+=2)ans+=(1.0/i);
	cout<<setprecision(2)<<fixed<<ans;
}