import java.util.Scanner;

public class Average {

    public static void main(String[] args) {
        Scanner input = new Scanner (System.in);
        System.out.println("please enter 3 enteger number :");
        int x = input.nextInt();
        int y = input.nextInt();
        int z = input.nextInt();
        int sum = x+y+z;
        double avg = sum/3.0;
        System.out.println(avg);
        
    }
}