#include <bits/stdc++.h>
#define int long long
using namespace std;
const int maxm=2e6+5;
double d[maxm];
int n;
void solve(){
    cin>>n;
    d[n]=0;
    for(int i=n-1;i>=1;i--){
        d[i]=d[i+1]+n*1.0/(n-i);
    }
    printf("%.10f\n",d[1]);
}
signed main(){
    solve();
    return 0;
}
/**
  *  author:    Apiram
  *  created:   06.03.2021 18:23:08  
**/
#pragma GCC target ("avx2")
#pragma GCC optimization ("O2")
#pragma GCC optimization ("unroll-loops")
#include<bits/stdc++.h>
using namespace std;
 
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
double n;
cin>>n;
cout<<setprecision(15)<<fixed;
double a=0;
for (int i =1;i<n;++i){
a+=n/i;
}
cout<<a;
return 0;}
	