import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    int score[] = new int[1000];

    while (true) {
      int n = scanner.nextInt();
      if (n == 0) break;
      double m = 0.0, d = 0.0;

      for (int i = 0; i < n; ++i) {
        score[i] = scanner.nextInt();
        m += score[i];
      }

      m /= n;

      for (int i = 0; i < n; ++i) {
        d += Math.pow(((double)score[i] - m), 2);
      }

      d /= n;

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

/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