#include<bits/stdc++.h>
using namespace std;

#define dvg(x) cout<<__LINE__<<": "<<#x<<" = "<<x<<endl;
#define endl "\n"
#define rep(i, st, n) for(int i = st; i <= n; i += 1)
#define ll long long
#define l64 int64_t
#define ld long double
#define ff first
#define ss second
#define pii pair<int, int>
#define pll pair<ll,ll>
#define pli pair<ll, int>
#define pil pair<int, ll>
#define pb(x) push_back(x)
#define pp() pop_back()
#define in(x) insert(x)
#define vi vector<int>
#define vll vector<ll>
#define vs vector<string>
#define vpii vector<pii>
#define vpll vector<Pll>
#define vvi vector<vi>
#define pn(n) cout<<n<<"\n";
#define pn2(x,y) cout<<x<<" "<<y<<"\n";
#define pr(ar) {for (auto i : ar) cout<<i<<" "; cout<<"\n";}
#define get(x) cin>>x;
#define get2(x, y) cin>>x>>y;
#define cn(v) for(auto &i : v) cin>>i;
#define sq(a) (a*a)
#define mem(x, y) memset(x, y, sizeof(x))

int dx[] {-1, 0, 1, 0, 1, 1, -1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, 1, -1};

int const N = 1e5 + 10;

void solve()
{
	double n; cin>>n;
	double ans = 0;
	for(int i = 1; i < n; i++) ans += 1.000/i;
	ans *= n;

	setprecision(12);
	cout<<fixed<<ans<<endl;
}

int main()
{ 
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int T = 1; 
	//
	while(T--)
	{	
		solve();
	}

	return 0;
} 

#include <bits/stdc++.h>
using namespace std;
typedef long long int lld;
typedef pair<int,int> pi;
typedef pair<lld,lld> pl;
typedef pair<int,lld> pil;
typedef pair<lld,int> pli;
typedef vector<int> vit;
typedef vector<vit> vitt;
typedef vector<lld> vlt;
typedef vector<vlt> vltt;
typedef vector<pi> vpit;
typedef vector<vpit> vpitt;
typedef long double ld;
#define x first
#define y second
#define pb push_back
#define all(v) v.begin(), v.end()
#define sz(x) (int)x.size()
#define mk(a,b) make_pair(a,b)
bool isrange(int y,int x,int n,int m){
	 if(0<=y&&y<n&&0<=x&&x<m) return true;
	 return false;
}
int dy[4] = {1,0,-1,0},dx[4]={0,1,0,-1},ddy[8] = {1,0,-1,0,1,1,-1,-1},ddx[8] = {0,1,0,-1,1,-1,1,-1};


void solve(int tc){
	int n;
	cin >> n;
	double ans = 0;
	for(int e=1;e<n;e++) ans += (double)n/(double)e;
	printf("%.9lf",ans);
}


int main(void){
	/*
	ios_base :: sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	*/
	int tc = 1;
	/*
		cin >> tc;
	*/
	for(int test_number=1;test_number<=tc;test_number++){
		solve(test_number);
	}
	return 0;
}