Rebjat ja vsjo sdelal s pervogo raza, prosto hotel sprosit esli etot kod mozhno Refactornut kaknibud , toest sdelat menshe ili effektivnei Blagodorju 
public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        int sum=0;
        double middle=0.0;
        int count=0;


        while(true){
            int a = Integer.parseInt(reader.readLine());

            if(a == -1){
                break;
            }else{
                sum +=a;
                count++;

            }
            middle = (double)sum / count;
        }
        System.out.println(middle);
    }
}