import java.text.DecimalFormat;
import java.util.Scanner;

public class Main{

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		double sum=0,inn;
		Scanner cin=new Scanner(System.in);
		int i=0;
			for(i=0;i<12;i++){
				inn=cin.nextDouble();
				sum+=inn;
}
		

		
		String parten = "#.##";
		DecimalFormat decimal = new DecimalFormat(parten);
		String str= decimal.format(sum/12.0);
				 System.out.print("$"+str);

	}

}