#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    int k; cin >> k;
    double ans = 0;
    if(k == 0){
        srep(i,1,1000001){
            ans += 1.0/i/i;
        }
        cout << fixed << setprecision(10) << ans << endl;
        return 0;
    }
    srep(i,1,k+1){
        ans += 1.0 / i;
    }
    ans /= (double)k;
    cout << fixed << setprecision(10) << ans << endl;
    return 0;
}