import java.io.*;
import java.util.*;
import java.text.DecimalFormat;
//import java.text.NumberFormat;

public class Main
{
            public static void main(String args[])
            {
                    Scanner cin;
                    double read=0;
                    double result=0;
                    DecimalFormat format=new DecimalFormat("#0.##");
                    
                       
                    
                    for(int count=1;count<=12;count++)
                    {
                    	
                    	cin=new Scanner(System.in);
                    	
                    	read=cin.nextDouble();
                    	result=result+read;
                    	
                    }
                    System.out.println("$"+format.format(result/12));	
                    	
                    	
            }
}