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