1154.java

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    int X,i;
    double soma;
    Scanner in = new Scanner(System.in);
    X = in.nextInt();
    soma = 0;
    i = 0;
    while(X>0){
    	soma = soma + X;
		  i = i + 1;
		  X = in.nextInt();
    }
    System.out.printf("%.2f\n",soma/i);
  }
}