// ITP1_10_C Standard_Deviation
import java.io.*;

class Main {
   public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz