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