import 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 sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  }
}
 import java.util.*; util.* java 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 sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    while(true) {
      int n = sc.nextInt();
      if (n == 0) {
        break;
      }
      int sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  } main {
    Scanner sc = new Scanner(System.in);
    while(true) {
      int n = sc.nextInt();
      if (n == 0) {
        break;
      }
      int sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true) {
      int n = sc.nextInt();
      if (n == 0) {
        break;
      }
      int sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    } true {
      int n = sc.nextInt();
      if (n == 0) {
        break;
      }
      int sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) {
        break;
      } n == 0 n 0 {
        break;
      } break; int sum = 0; sum 0 int[] stu = new int[n]; stu new int[n] n for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        stu[i] = sc.nextInt();
        sum += stu[i];
      } {
        stu[i] = sc.nextInt();
        sum += stu[i];
      } stu[i] = sc.nextInt() stu[i] stu i sc.nextInt() sc.nextInt sc sum += stu[i] sum stu[i] stu i double ave = sum / (double) n; ave sum / (double) n sum (double) n double dveSum = 0.0; dveSum 0.0 for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        dveSum += Math.pow(stu[i] - ave, 2);
      } {
        dveSum += Math.pow(stu[i] - ave, 2);
      } dveSum += Math.pow(stu[i] - ave, 2) dveSum Math.pow(stu[i] - ave, 2) Math.pow Math stu[i] - ave stu[i] stu i ave 2 double dve = Math.sqrt(dveSum / (double) n); dve Math.sqrt(dveSum / (double) n) Math.sqrt Math dveSum / (double) n dveSum (double) n System.out.println(dve) System.out.println System.out System System.out dve 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 sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  }
} 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 sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  }
} Main
import 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 sum = 0;
      int[] stu = new int[n];
      for(int i = 0; i < n; i++) {
        stu[i] = sc.nextInt();
        sum += stu[i];
      }
      double ave = sum / (double) n;
      double dveSum = 0.0;
      for(int i = 0; i < n; i++) {
        dveSum += Math.pow(stu[i] - ave, 2);
      }
      double dve = Math.sqrt(dveSum / (double) n);
      System.out.println(dve);
    }
  }
}

