import java.util.Scanner;
import java.text.DecimalFormat;
public class Main {
public static void main(String[] args){
Scanner input=new Scanner(System.in);
double sum=0;
for(int i=1;i<=12;i++){
if(input.hasNext()==false)return;
double one=input.nextFloat();
sum+=one;
}
double ave=sum/12.0;
DecimalFormat df=new DecimalFormat("#.00");
System.out.println("$"+df.format(ave));
}
}