#include <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < n; i++)
#define ll long long
using namespace std;

int main(){
    int n;
    cin >> n;
    double ans = 0;
    rep(i, n){
        if (i==n-1) break;
        double i_ans = n / double(n-i-1);
        ans += i_ans;
    }
    printf("%.10f\n", ans);
} 
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define NDEBUG
#define eprintf(...) do {} while (0)
#endif
#include<cassert>

using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
#define rprintf(fmt, begin, end) do { const auto end_rp = (end); auto it_rp = (begin); for (bool sp_rp=0; it_rp!=end_rp; ++it_rp) { if (sp_rp) putchar(' '); else sp_rp = true; printf(fmt, *it_rp); } putchar('\n'); } while(0)

int N;
using Double = long double;

void MAIN() {
    scanf("%d", &N);

    Double e = 0;
    for (int i=N-1; i>=1; i--) {
	e = e + (Double)(N) / i;
    }
    printf("%.20f\n", (double)e);
}

int main() {
    int TC = 1;
//    scanf("%d", &TC);
    REP (tc, TC) MAIN();
    return 0;
}

