#include<bits/stdc++.h>
//#include"atcoder/all"
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define all(a) (a).begin(),(a).end()
using namespace std;
//using namespace atcoder; 
int main(){
  long double ans = 0;
  int k,i;scanf("%d",&k);
  if(k == 0){
    for(i=1;i<=10000000;i++) ans += (long double)(1)/i/i;
    printf("%Lf\n",ans);
    return 0;
  }
  for(i=1;i<=k;i++) ans += (long double)(1)/i;
  printf("%Lf\n",ans/k);
}