#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acos(-1.0);

ll mod_pow(ll x, ll n,ll m) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n % mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 17;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}

struct edge {
	int to;
};
struct Centroid_Decomposition {
private:
	int n;
	vector<vector<edge>> G;

	vector<vector<int>> fG; int root;
	vector<vector<vector<int>>> dists;
	vector<vector<vector<int>>> rdists;
	vector<vector<int>> pdist, rpdist;
public:
	Centroid_Decomposition(int n_) {
		n = n_;
		G.resize(n);

		fG.resize(n); root = -1;
		dists.resize(n);
		rdists.resize(n);
	}
	void add_edge(int a, int b) {
		G[a].push_back({ b });
		G[b].push_back({ a });
	}

	void complete(int sup) {
		vector<bool> exi(n, false);
		vector<int> ori(n); rep(i, n)ori[i] = i;
		queue<vector<int>> q;
		queue<int> que;
		
		q.push(ori);
		que.push(-1);

		function<int(int, int,int&,int&)> szdfs=[&](int id, int fr,int &g,int &sz)->int {
			int res = 1;
			int ma = 0;
			for (edge e : G[id]) {
				if (!exi[e.to])continue;
				if (e.to == fr)continue;
				int nex = szdfs(e.to, id, g, sz);
				ma = max(ma, nex);
				res += nex;
			}
			if (ma <= sz / 2 && sz - res <= sz / 2)g = id;
			return res;
		};

		function<int(vector<int>)> cdfs = [&](vector<int> v)->int {
			for (int id : v) {

			}
		};
		while (!q.empty()) {
			vector<int> v = q.front(); q.pop();
			int par = que.front(); que.pop();
			if (v.empty())continue;

			int g;
			for (int id : v) {
				exi[id] = true;
			}
			int sz = v.size();
			szdfs(v[0], -1, g, sz);
			if (par >= 0) {
				fG[par].push_back(g);
			}
			else {
				root = g;
			}

			for (edge e : G[g]) {
				if (!exi[e.to])continue;

			}


			for (int id : v) {
				exi[id] = false;
			}
		}
	}
};

ld f(ld x) {
	if (x == 0)return 1;
	else return (sinl(x) / x) * (sinl(x) / x);
}
const ld y = 0.0000001000;
void solve(){
	ld x; cin >> x;
	ld ans = 0;
	for (int i = 0; i <= 5000000; i++) {
		ans += f(x + i);
	}
	ans += y;
	cout << ans << "\n";
}




signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(10);
	//init_f();
	//cout << grandy(2, 3, false, false) << "\n";
	//int t; cin >> t; rep(i, t)
	solve();
	return 0;
}