#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#include <atcoder/dsu>
#include <atcoder/segtree>
using namespace atcoder;
using namespace std;
typedef long long ll;
#define rep(i,a,b) for(int i=a;i<b;i++)
using vi = vector<int>; 
using vvi = vector<vi>; 
using li =vector<ll>;
using lli=vector<li>;
using si =vector<char>;
using ssi =vector<si>;
const long long INF = 1e18;
const long long MOD=1e9+7;
//for (auto [key, val] : mp)
int main() {
	long double k;cin>>k;
	long double ans=0.0;
	if(k==0)printf("%.12llf\n",1.644934057834575);

for(long double i=1;i<=k;i+=1.0){
	ans=ans+1.0/i;
}

ans=ans*(1.0)/k;
printf("%.12llf\n",ans);
}