

#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector <int> vi;
typedef vector <vi> vii;
typedef vector <string> vs;
typedef vector <ll> vll;

#define LSB(x) x&(-x)
#define endl "\n"
#define quick ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define f(a,b,c) for(ll (a)=(b);(a)<(c);++(a))
#define fi(a,b,c) for(ll (a)= (b);(a)<=(c);++(a))
#define fe(a,b) for(auto &(a) : (b))
#define fr(i,a,b) for(ll (i)=(a);(i)>(b);(i)--)
#define r(a,b) f(a,0,b)
#define v vector
#define SUM(x,s) for(ll i=0;i<(x).size();i++)(s)+=(x)[i];
#define F first
#define S second
#define pb push_back
#define mp make_pair
#define ALL(x) x.begin(),x.end()
#define SORT(x) sort(ALL(x))
#define TC(t) while(t--)
#define unS unordered_set
#define unM unordered_map
#define oS set
#define oM map
#define eb emplace_back
#define pq priority_queue
#define print(x) cout<<(x)<<endl



///////////////////// I/O shortcuts ////////////////////////////////
template <typename D>
istream& operator>> (istream &in , vector <D> &arr) {
    ll n = arr.size();
    r(i, n) {
        in >> arr[i];
    }
    return in;
}

template <typename D>
ostream& operator<< (ostream &in , vector <D> &arr) {
    for (auto x : arr) in << x << " ";
    in << endl;
    return in;
}
template <typename D, typename B>
ostream& operator<< (ostream &in , pair <D, B> &p) {
    in << p.F << " " << p.S << endl;
    in << endl;
    return in;
}


////////////////////////////Global Variables////////////////////////////////
ll i, j, k, l, x, y, z, m, n, a, b, c, r, d, t = 1;


string s;
template<typename A, typename B> A max(A a, B b) {return (a > b) ? a : b;}
template<typename A, typename B> A min(A a, B b) {return (a < b) ? a : b;}
/////////// The Code Starts Here ///////////////////////////////////////

void solve(int tc) {
    cin >> n;
    ll ans = 0;
    f(i, 1, n) {
        ll s = n - i;
        if (s > 0) ans++;
        else break;
    }
    cout << ans << endl;

}

///////////////////////////////////////////////////////////




int main() {
    quick;
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    // cin >> t;
    int k = 1;

    TC(t) solve(k++);



}
#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;
typedef long long LL;
int n;
int main() {
    cin >> n;
    double res = 0;
    for (int i = 1; i <= n-1; i++) {
        res += 1.0 * n / i;
    }
    printf("%.10lf\n", res);
    return 0;
}