#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const int m=1000000;
int main()
{
	double x; cin>>x;
	if(x<1e-9){
		printf("2.07079632677096370230\n");
		return 0;
	}
	double ans=sin(x)/x*sin(x)/x;
	double s1=1.0/(x+1);
	for(int i=1; i<m; i++){
		s1+=1.0/(x+i)/(x+i)/(x+i+1);
	}
	for(int i=1; i<m; i++){
		s1-=cos(2*(x+i))/(x+i)/(x+i);
	}
	ans+=s1/2;
	printf("%.10lf\n", ans);
	return 0;
}