import java.io.*;
import java.util.*;
import java.lang.*;

class Main{
  public static void main(String[] args) throws IOException{
    Scanner scan=new Scanner(System.in);
    while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    }
  }
}
 import java.io.*; io.* java import java.util.*; util.* java import java.lang.*; lang.* java class Main{
  public static void main(String[] args) throws IOException{
    Scanner scan=new Scanner(System.in);
    while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    }
  }
} Main public static void main(String[] args) throws IOException{
    Scanner scan=new Scanner(System.in);
    while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    }
  } main {
    Scanner scan=new Scanner(System.in);
    while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    }
  } Scanner scan=new Scanner(System.in); scan new Scanner(System.in) while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    } true {
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    } int n=Integer.parseInt(scan.next()); n Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan if(n==0)break; n==0 n 0 break; int[] s=new int[n]; s new int[n] n for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      } int i=0; int i=0; i 0 i<n i n i++ i++ i {
        s[i]=Integer.parseInt(scan.next());
      } {
        s[i]=Integer.parseInt(scan.next());
      } s[i]=Integer.parseInt(scan.next()) s[i] s i Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan double sum=0; sum 0 double sum2=0; sum2 0 for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      } int i=0; int i=0; i 0 i<n i n i++ i++ i {
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      } {
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      } sum+=s[i] sum s[i] s i sum2+=Math.pow(s[i],2) sum2 Math.pow(s[i],2) Math.pow Math s[i] s i 2 double avg=sum/n; avg sum/n sum n double dev=Math.sqrt(sum2/n-Math.pow(avg,2)); dev Math.sqrt(sum2/n-Math.pow(avg,2)) Math.sqrt Math sum2/n-Math.pow(avg,2) sum2/n sum2 n Math.pow(avg,2) Math.pow Math avg 2 System.out.println(dev) System.out.println System.out System System.out dev String[] args args
import java.io.*;
import java.util.*;
import java.lang.*;

class Main{
  public static void main(String[] args) throws IOException{
    Scanner scan=new Scanner(System.in);
    while(true){
      int n=Integer.parseInt(scan.next());
      if(n==0)break;
      int[] s=new int[n];
      for(int i=0;i<n;i++){
        s[i]=Integer.parseInt(scan.next());
      }
      double sum=0;
      double sum2=0;
      for(int i=0;i<n;i++){
        sum+=s[i];
        sum2+=Math.pow(s[i],2);
      }
      double avg=sum/n;
      double dev=Math.sqrt(sum2/n-Math.pow(avg,2));
      System.out.println(dev);
    }
  }
}

