text: ﻿#include <iostream>
  #include <math.h>
  using namespace std;
  int main() {
  long double b,a;
  while(scanf("%Lf",&b)!=EOF) {
  a=(b*(sin(1.88495559215)))/(sin(1.09955742876));
  printf("%.10Lf\n",a);
  	}
  return 0;	
  }