#include "bits/stdc++.h"
using namespace std;
using     ll=long long;
using    vll=vector<   ll>;
using   vvll=vector<  vll>;
using  vvvll=vector< vvll>;
using vvvvll=vector<vvvll>;
using     dd=double;
using    vdd=vector<   dd>;
using   vvdd=vector<  vdd>;
using pll=pair<ll,ll>; using tll=tuple<ll,ll,ll>; using qll=tuple<ll,ll,ll,ll>;
using   vpll=vector<  pll>;

constexpr ll INF = 1LL << 60;
struct Fast{ Fast(){ cin.tie(0); ios::sync_with_stdio(false); cout<<fixed<<setprecision(numeric_limits<double>::max_digits10); } } fast;
#define REPS(i, S, E) for (ll i = (S); i <= (E); i++)
#define REP(i, N) REPS(i, 0, (N)-1)
#define DEPS(i, S, E) for (ll i = (E); i >= (S); i--)
#define DEP(i, N) DEPS(i, 0, (N)-1)
#define rep(i, S, E)  for (ll i = (S); i <= (E); i++)
#define dep(i, E, S)  for (ll i = (E); i >= (S); i--)
#define each(e, v) for (auto&& e : v)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
template<class T> inline T MaxE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmax(m,v[i]); return m; }
template<class T> inline T MinE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmin(m,v[i]); return m; }
template<class T> inline T MaxE(vector<T> &v) { return MaxE(v,0,(ll)v.size()-1); }
template<class T> inline T MinE(vector<T> &v) { return MinE(v,0,(ll)v.size()-1); }
template<class T> inline T Sum(vector<T> &v,ll S,ll E){ T s=T(); rep(i,S,E)s+=v[i]; return s; }
template<class T> inline T Sum(vector<T> &v) { return Sum(v,0,v.size()-1); }
template<class T> inline ll sz(T &v){ return (ll)v.size(); }
inline ll CEIL(ll a,ll b){ return (a<0) ? -(-a/b) : (a+b-1)/b; }
inline ll FLOOR(ll a,ll b){ return -CEIL(-a,b); }

template<ll MOD> struct mll_{
	ll val;
	mll_(ll v = 0): val(v % MOD){ if (val < 0) val += MOD; }
	mll_ operator - () const { return -val; }
	mll_ operator + (const mll_ &b) const { return val + b.val; }
	mll_ operator - (const mll_ &b) const { return val - b.val; }
	mll_ operator * (const mll_ &b) const { return val * b.val; }
	mll_ operator / (const mll_ &b) const { return mll_(*this) /= b; }
	mll_ operator + (ll b) const { return *this + mll_(b); }
	mll_ operator - (ll b) const { return *this - mll_(b); }
	mll_ operator * (ll b) const { return *this * mll_(b); }
	friend mll_ operator + (ll a,const mll_ &b) { return b + a; }
	friend mll_ operator - (ll a,const mll_ &b) { return -b + a; }
	friend mll_ operator * (ll a,const mll_ &b) { return b * a; }
	friend mll_ operator / (ll a,const mll_ &b) { return mll_(a)/b; }
	mll_ &operator += (const mll_ &b) { val=(val+b.val)%MOD; return *this; }
	mll_ &operator -= (const mll_ &b) { val=(val+MOD-b.val)%MOD; return *this; }
	mll_ &operator *= (const mll_ &b) { val=(val*b.val)%MOD; return *this; }
	mll_ &operator /= (const mll_ &b) {
		ll c=b.val,d=MOD,u=1,v=0;
		while (d){
			ll t = c / d;
			c -= t * d; swap(c,d);
			u -= t * v; swap(u,v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll_ &operator += (ll b) { return *this += mll_(b); }
	mll_ &operator -= (ll b) { return *this -= mll_(b); }
	mll_ &operator *= (ll b) { return *this *= mll_(b); }
	mll_ &operator /= (ll b) { return *this /= mll_(b); }
	bool operator == (const mll_ &b) const { return val == b.val; }
	bool operator != (const mll_ &b) const { return val != b.val; }
	bool operator == (ll b) const { return *this == mll_(b); }
	bool operator != (ll b) const { return *this != mll_(b); }
	friend bool operator == (ll a,const mll_ &b) { return mll_(a) == b.val; }
	friend bool operator != (ll a,const mll_ &b) { return mll_(a) != b.val; }
	friend ostream &operator << (ostream &os,const mll_ &a) { return os << a.val; }
	friend istream &operator >> (istream &is,mll_ &a) { return is >> a.val; }
	static mll_ Combination(ll a,ll b){
		chmin(b,a-b);
		if (b<0) return mll_(0);
		mll_ c = 1;
		rep(i,0,b-1) c *= a-i;
		rep(i,0,b-1) c /= i+1;
		return c;
	}
};
using mll = mll_<998244353LL>;
using vmll    = std::vector<mll>;
using vvmll   = std::vector<vmll>;
using vvvmll  = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

template<class T> struct MatG{
	ll h=0, w=0; //h行w列
	vector<vector<T>> mat;
	MatG(){}
	MatG(ll h_, ll w_, T x) { init(h_, w_, x); }
	MatG(ll h_, ll w_) { init(h_, w_); }
	MatG(ll h_, ll w_, string c) { init(h_, w_, c); }
	void init(ll h_, ll w_, T x){ h=h_; w=w_; mat.assign(h, vector<T>(w,x)); }
	void init(ll h_, ll w_){ init(h_,w_,T()); }
	void init(ll h_, ll w_, string c){ init(h_, w_); if(c=="E")E(); }
	ll H() const { return h; }
	ll W() const { return w; }
	bool invalid() const { return mat.empty(); }
	vector<T> &operator[](ll i) { return mat[i]; }
	const vector<T> &operator[](ll i) const { return mat[i]; }
	MatG<T> &operator+=(const MatG<T> &B) {REP(i,h)REP(j,w) mat[i][j]+=B[i][j];return *this;}
	MatG<T> operator+(const MatG<T> &B) const {return MatG<T>(*this) += B;}
	MatG<T> operator*(const MatG<T> &B) const {
		MatG<T> ret(h, B.W());
		REP(i, h) REP(j, B.W()) REP(k, w) ret[i][j] += mat[i][k] * B[k][j];
		return move(ret);
	}
	vector<T> operator*(const vector<T> &v) const {
		vector<T> ret(v.size());
		REP(i, this->h) REP(j, this->w) ret[i] += this->mat[i][j] * v[j];
		return move(ret);
	}
	MatG<T> Pow(ll N) const {
		MatG<T> ret(*this), a(*this);
		for (ll n=N-1; n>0; n>>=1, a=a*a){ if (n&1) ret=ret*a; }
		return move(ret);
	}
	MatG<T> t() const {
		MatG<T> ret(this->w, this->h);
		REP(i, this->w) REP(j, this->h) ret[i][j] = this->mat[j][i];
		return move(ret);
	}
	void E(){ rep(i, 0, min(h,w)-1) mat[i][i]=1; }
#if defined(_DEBUG)
	void dump() { ::dump(mat); }
#endif
	MatG(MatG<T> &&B){ *this=move(B); } //以下、ムーブ対応
	MatG(MatG<T> const &B){ *this=B; }
	MatG<T> &operator=(MatG<T> &&B){ h=B.h; w=B.w; mat.swap(B.mat); return *this; }
	MatG<T> &operator=(MatG<T> const &B){ h=B.h; w=B.w; mat=B.mat; return *this; }
};
using Mat = MatG<mll>;


#if 0
#include <atcoder/all>
using namespace atcoder;
#endif

dd pi=3.14159265358979;
void solve()
{
	ll k;  cin >> k;

	if (k==0){
		cout << pi*pi/6. << '\n';return;
	}

	dd ans=0.;
	rep(i,1,k){
		ans+=1./i;
	}
	cout << ans/k << '\n';
}

int main(){
#if 1
	solve();

#else
	ll t;  cin >> t;
	rep(i, 0, t-1){
		solve();
	}
#endif
	return 0;
}