public class Solution { public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); double result = 0.0f; int sum = 0; int i = 0; while(true) { String numbers = br.readLine(); int num = Integer.parseInt(numbers); if(num == -1) { break; } if(num != 0) { sum += num; i++; } } if(sum == 0) { result = 0.0; } else { result = (double)sum/(double)i; } System.out.print(result); } }