#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <cmath>

double f(double x) {
  if (abs(x)<1e-9) {
    return 1;
  } else {
    double v=std::sin(x)/x;
    return v*v;
  }
}
int main() {
  double ans=0;
  int n=(int)1e6;
  double x;
  std::cin>>x;
  for (int i=0;i<n;++i) ans+=f(i+x);
  ans+=1/(2*(x+n+0.5));
  printf("%.20f\n", ans);
}