import java.text.DecimalFormat;
import java.util.Scanner;
 
class Main{
	public static void main(String[] args){
		Scanner in=new Scanner(System.in);
		int len=12;
		double sum=0;
		while(len--!=0){
			sum+=in.nextDouble();
		}
		DecimalFormat df=new DecimalFormat();
		df.setMaximumFractionDigits(2);
		df.setMinimumFractionDigits(2);
		System.out.println("$"+df.format(sum/12).replaceAll(",", ""));
	}
}