package com.javarush.task.task05.task0507;
/*
Среднее арифметическое
*/
public class Solution {
public static void main(String[] args) throws Exception {
//напишите тут ваш ко
BufferedReader number = new BufferedReader(new InputStreamReader(System.in));
double sum = 0;
int count = 0;
while(true){
int n = Integer.parseInt(number.readLine());
if (n==-1)
break;
}
sum = sum + n;
count++;
int s = sum/count;
System.out.println (s);
}
}