//The sum

#include <iostream>
#include <math.h>

int power(double a, int b)
{
  for(int i=0;i<=b;i++)
    {
      a=a*a;
    }
}

int main () {
		
  double s=0.0;

  for(int i=0;i<=2;i++)
    {
      s=s+power(0.5,i);
      //std::cout<<s;
    }
  std::cout<<"\n"<<s <<std::endl;
}