#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cmath>
const int replim=1e7+9;
double x,ans,base;
int main(){
  std::cin>>x;
  std::cout<<std::setprecision(10)<<std::fixed;
  ans=std::sin(x)/x*std::sin(x)/x;
  base=1./(x+1.);
  for(int cx=1;cx<=replim;++cx)
    base+=1./(x+cx)/(x+cx)/(x+cx+1);
  for(int cx=1;cx<=replim;++cx)
    base-=std::cos(2*(x+cx))/(x+cx)/(x+cx);
  ans+=.5*base;
  std::cout<<ans<<std::endl;
  return 0;
}