//Bismillahirrahmanirrahim
#include"bits/stdc++.h"
using namespace std;
#define ll long long
#define sz(i) (int)i.size()
#define ln "\n"
const int N = 2e5+5;
void solve(){
	string s; cin >> s;
	string ans;
	for(int i =0; i < s.size(); i++){
		if(s[i] != '.')
			ans+=s[i];
		else
			break;
	}
	cout << ans << endl;
}

int main(){
	ios_base::sync_with_stdio(false); cin.tie(nullptr);
	int t=1; //cin >> t;
	while(t--) solve();
}


#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
const ll INF=1LL<<60;
const double EPS = 1e-10;
const ll mod=1000000007;
//const ll mod=998244353;

int main(void){
    ll n;
    cin>>n;
    double ans=0;
    for(int i=1;i<n;i++){
        ans+=double(n)/double(i);
    }
    printf("%.10lf\n",ans);
}