public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int sum = 0;
int n = 0;
double rez = 0;
while(true){
int a = Integer.parseInt(reader.readLine());
if(a == (-1)) {break;}
else {
n++;
sum = sum + a;
rez = sum/n;}
}
System.out.println(rez);
package com.javarush.task.task05.task0507;
import java.io.BufferedReader;
import java.io.InputStreamReader;
/*
Среднее арифметическое
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int sum = 0;
int n = 0;
double rez = 0;
while(true){
int a = Integer.parseInt(reader.readLine());
if(a == (-1)) {break;}
else {
n++;
sum = sum + a;
rez = sum/n;}
}
System.out.println(rez);
}
}