import  java.util.Scanner;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  }
} 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 = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  } main {
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    } true {
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    } int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc if(n == 0) break; n == 0 n 0 break; int a[] = new int[n]; a new int[n] n double sum = 0; sum 0 double sum2 = 0; sum2 0 for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      } {
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      } a[i] = Integer.parseInt(sc.next()) a[i] a i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc sum += a[i] sum a[i] a i sum2 += a[i] * a[i] sum2 a[i] * a[i] a[i] a i a[i] a i double a1 = sum2 / n; a1 sum2 / n sum2 n double a2 = (sum / n) * (sum / n); a2 (sum / n) * (sum / n) (sum / n) sum n (sum / n) sum n System.out.printf("%f\n", Math.sqrt(a1 - a2)) System.out.printf System.out System System.out "%f\n" Math.sqrt(a1 - a2) Math.sqrt Math a1 - a2 a1 a2 String[] args args public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  }
} public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  }
} Main
import  java.util.Scanner;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int n = Integer.parseInt(sc.next());
      if(n == 0) break;
      int a[] = new int[n];
      double sum = 0;
      double sum2 = 0;
      for(int i = 0; i < n; i++){
        a[i] = Integer.parseInt(sc.next());
        sum += a[i];
        sum2 += a[i] * a[i];
      }
      double a1 = sum2 / n;
      double a2 = (sum / n) * (sum / n);
      System.out.printf("%f\n", Math.sqrt(a1 - a2));
    }
  }
}
