import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  }

} import java.util.Scanner; Scanner java.util public class Main {

  public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  }

} Main public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  } main {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  } Scanner stdin = new Scanner(System.in); stdin new Scanner(System.in) while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    } true {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    } int n = stdin.nextInt(); n stdin.nextInt() stdin.nextInt stdin if (n == 0) {
        break;
      } n == 0 n 0 {
        break;
      } break; int[] arr = new int[n]; arr new int[n] n double m = 0; m 0 for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        arr[i] = stdin.nextInt();
        m += arr[i];
      } {
        arr[i] = stdin.nextInt();
        m += arr[i];
      } arr[i] = stdin.nextInt() arr[i] arr i stdin.nextInt() stdin.nextInt stdin m += arr[i] m arr[i] arr i m /= n m n double a = 0; a 0 for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        a += Math.pow(arr[i] - m, 2);
      } {
        a += Math.pow(arr[i] - m, 2);
      } a += Math.pow(arr[i] - m, 2) a Math.pow(arr[i] - m, 2) Math.pow Math arr[i] - m arr[i] arr i m 2 System.out.printf("%f%n", Math.sqrt(a / n)) System.out.printf System.out System System.out "%f%n" Math.sqrt(a / n) Math.sqrt Math a / n a n String[] args args public class Main {

  public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  }

} public class Main {

  public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  }

} Main
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner stdin = new Scanner(System.in);
    while (true) {
      int n = stdin.nextInt();
      if (n == 0) {
        break;
      }

      int[] arr = new int[n];
      double m = 0;
      for (int i = 0; i < n; i++) {
        arr[i] = stdin.nextInt();
        m += arr[i];
      }
      m /= n;

      double a = 0;
      for (int i = 0; i < n; i++) {
        a += Math.pow(arr[i] - m, 2);
      }

      System.out.printf("%f%n", Math.sqrt(a / n));
    }
  }

}