#include <bits/stdc++.h>

using namespace std;

int main(){
    int n; cin >> n;
    double ans = 0;
    for (int i = 1; i <= n-1; i++){
        ans += 1.0*n/i;
    }
    cout << fixed << setprecision(8) << ans << endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef long long ll;
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n)  FOR(i,0,n)
const double EPS = 1e-10;
const double PI  = acos(-1.0);
#define CLR(a) memset((a), 0 ,sizeof(a))
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
bool compare_by_b(pair<LL, LL> a, pair<LL, LL> b) {
    if(a.second != b.second)return a.second < b.second;
    else return a.first < b.first;
}


void solve(long long N){
    double ret = 0;
    for(int i= N-1; i >=1; i--){
        ret+=(double)N/(double)i;
    }
    cout<<setprecision(12)<<ret<<endl;
    return;
}

int main(){
    long long N;
    scanf("%lld",&N);
    solve(N);
    return 0;
}
