#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define mod 1e9
#define vll vector<ll>
#define pb push_back
#define what_is(x) cerr << #x << " is " << x << endl;
using namespace std;
inline void sol() {}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  int k;
  cin>>k;
  double ans = 0;
  for(int i=1;i<=1e7;i++){
    ans += 1.0/(i*1.0*(k+i*1.0));
  }
  printf("%0.07f",ans);

  return 0;
}