import java.util.Scanner;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = sc.nextInt();
      if(n==0){
        break;
      }
      int[] scores = new int[n];
      for(int i=0;i<scores.length;i++){
        scores[i]=sc.nextInt();
      }
      double average=0,variance=0;
      for(int i=0;i<scores.length;i++){
        average+=(double)scores[i]/n;
      }
      for(int i=0;i<scores.length;i++){
        variance+=(double)(scores[i]-average)*(scores[i]-average)/n;
      }
    System.out.println(Math.sqrt(variance));
    }
  }
}
/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