import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  }
}
 import java.util.Scanner; Scanner java.util public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  } main {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n int[] score; score while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    } true {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    } n = sc.nextInt() n sc.nextInt() sc.nextInt sc if (n == 0)
        break; n == 0 n 0 break; score = new int[n] score new int[n] n int sum = 0; sum 0 for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      } {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      } int s = sc.nextInt(); s sc.nextInt() sc.nextInt sc score[i] = s score[i] score i s sum += s sum s double tmp = 0; tmp 0 for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      } {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      } tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n) tmp ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n) ((double)score[i] - (double)sum / n) (double)score[i] score i (double)sum / n (double)sum n ((double)score[i] - (double)sum / n) (double)score[i] score i (double)sum / n (double)sum n System.out.printf("%.8f\n", Math.sqrt(tmp / n)) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(tmp / n) Math.sqrt Math tmp / n tmp n String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n;
    int[] score;
    while (true) {
      n = sc.nextInt();
      if (n == 0)
        break;
      score = new int[n];
      int sum = 0;
      for (int i = 0; i < n; i++) {
        int s = sc.nextInt();
        score[i] = s;
        sum += s;
      }
      double tmp = 0;
      for (int i = 0; i < n; i++) {
        tmp += ((double)score[i] - (double)sum / n) * ((double)score[i] - (double)sum / n);
      }
      System.out.printf("%.8f\n", Math.sqrt(tmp / n));
    }
  }
}

