// ITP1_10_C Standard_Deviation
import java.io.*;

class Main {
   public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   }
} import java.io.*; io.* java class Main {
   public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   }
} Main public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   } main {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      } catch (Exception e) {
         e.printStackTrace();
      } Exception e {
         e.printStackTrace();
      } e.printStackTrace() e.printStackTrace e {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      } while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         } true {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         } int n = Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if (n == 0) break; n == 0 n 0 break; double sum = 0; sum 0 double sumx = 0; sumx 0 double ave = 0; ave 0 String[] input = br.readLine().split(" "); input br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " double[] s = new double[n]; s new double[n] n for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            } {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            } s[i] = Double.parseDouble(input[i]) s[i] s i Double.parseDouble(input[i]) Double.parseDouble Double input[i] input i sum += s[i] sum s[i] s i ave = sum / n ave sum / n sum n for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
               sumx += Math.pow((s[i] - ave), 2) / n;
            } {
               sumx += Math.pow((s[i] - ave), 2) / n;
            } sumx += Math.pow((s[i] - ave), 2) / n sumx Math.pow((s[i] - ave), 2) / n Math.pow((s[i] - ave), 2) Math.pow Math (s[i] - ave) s[i] s i ave 2 n System.out.println(Math.sqrt(sumx)) System.out.println System.out System System.out Math.sqrt(sumx) Math.sqrt Math sumx String[] args args
// ITP1_10_C Standard_Deviation
import java.io.*;

class Main {
   public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

      try {
         while (true) {
            int n = Integer.parseInt(br.readLine());
            if (n == 0) break;

            double sum = 0;
            double sumx = 0;
            double ave = 0;

            String[] input = br.readLine().split(" ");
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
               s[i] = Double.parseDouble(input[i]);
               sum += s[i];
            }

            ave = sum / n;

            for (int i = 0; i < n; i++) {
               sumx += Math.pow((s[i] - ave), 2) / n;
            }

            System.out.println(Math.sqrt(sumx));
         }
      }

      catch (Exception e) {
         e.printStackTrace();
      }
   }
}