import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scanner = new Scanner(System.in);
    int[] data = new int[1000];
    while(true){
      int sum = 0;
      double p = 0;
      double ave;
      int n = scanner.nextInt();
    for (int i = 0; i < n; i++){
      int a = scanner.nextInt();
      data[i] = a;
      sum += a;
    }
    if(n == 0) break;
    ave = (double)sum / n;
    for(int i = 0; i < n; i++){
      p += ((double)data[i] - ave)*((double)data[i] - ave);
    }
    p /= n;
    double s = Math.sqrt(p);
    System.out.printf("%.8f\n", s);
  }
  }
}
/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