import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner in = new Scanner(System.in);
		double S,s1,s2;
		s1=(1.0/2.0)/(1.0-(1.0/2.0));
		s2=(1.0/3.0)/(1.0-(1.0/3.0));
		S=s1+s2;
		System.out.print(S);
	}
}