#include <stdio.h>
#include <math.h>
int main(){
  double s = 0, dz = -0.000001, z = 0, lim = -(1+sqrt(5))/2;
  while(z > lim) {z+=dz; s += dz * log(1-z)/z;}
  printf("%19.16f\n", -s);
  return 0;}
// yields -1.2185250647848354