import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Scanner;
import java.util.StringTokenizer;

public class Main {
  static InputReader in;
  static PrintWriter out;
  
  static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
}


  public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
}


  static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  }

} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Scanner; Scanner java.util import java.util.StringTokenizer; StringTokenizer java.util public class Main {
  static InputReader in;
  static PrintWriter out;
  
  static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
}


  public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
}


  static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  }

} Main static InputReader in; in static PrintWriter out; out public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
} main {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
} in = new InputReader(System.in) in new InputReader(System.in) out = new PrintWriter(System.out) out new PrintWriter(System.out) Solution solver = new Solution(); solver new Solution() solver.solve() solver.solve solver out.close() out.close out String[] args args static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
} Solution void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    } solve {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    } while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      } true {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      } int n = in.nextInt(); n in.nextInt() in.nextInt in if (n == 0) {
          break;
        } n == 0 n 0 {
          break;
        } break; double variance = 0; variance 0 double stddev; stddev double sum = 0; sum 0 double avg; avg double[] score = new double[n]; score new double[n] n for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
          score[i] = in.nextDouble();
          sum += score[i];
        } {
          score[i] = in.nextDouble();
          sum += score[i];
        } score[i] = in.nextDouble() score[i] score i in.nextDouble() in.nextDouble in sum += score[i] sum score[i] score i avg = sum / n avg sum / n sum n for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
          variance += Math.pow(score[i] - avg, 2);
        } {
          variance += Math.pow(score[i] - avg, 2);
        } variance += Math.pow(score[i] - avg, 2) variance Math.pow(score[i] - avg, 2) Math.pow Math score[i] - avg score[i] score i avg 2 variance /= n variance n stddev = Math.sqrt(variance) stddev Math.sqrt(variance) Math.sqrt Math variance out.printf("%.5f\n", stddev) out.printf out "%.5f\n" stddev static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  } InputReader public BufferedReader br; br public StringTokenizer st; st public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    } InputReader {
      br = new BufferedReader(new InputStreamReader(stream));
    } br = new BufferedReader(new InputStreamReader(stream)) br new BufferedReader(new InputStreamReader(stream)) InputStream stream stream public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    } nextInt {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    } while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
        st = new StringTokenizer(br.readLine());
      } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return Integer.parseInt(st.nextToken()); Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    } nextLong {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    } while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
        st = new StringTokenizer(br.readLine());
      } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return Long.parseLong(st.nextToken()); Long.parseLong(st.nextToken()) Long.parseLong Long st.nextToken() st.nextToken st public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    } next {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    } while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
        st = new StringTokenizer(br.readLine());
      } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    } nextDouble {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    } while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
        st = new StringTokenizer(br.readLine());
      } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return Double.parseDouble(st.nextToken()); Double.parseDouble(st.nextToken()) Double.parseDouble Double st.nextToken() st.nextToken st public class Main {
  static InputReader in;
  static PrintWriter out;
  
  static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
}


  public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
}


  static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  }

} public class Main {
  static InputReader in;
  static PrintWriter out;
  
  static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
}


  public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
}


  static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  }

} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Scanner;
import java.util.StringTokenizer;

public class Main {
  static InputReader in;
  static PrintWriter out;
  
  static class Solution {
    void solve() throws IOException {
      while (true) {
        int n = in.nextInt();
        if (n == 0) {
          break;
        }
        double variance = 0;
        double stddev;
        double sum = 0;
        double avg;
        
        double[] score = new double[n];
        for (int i = 0; i < n; i++) {
          score[i] = in.nextDouble();
          sum += score[i];
        }
        avg = sum / n;
        
        for (int i = 0; i < n; i++) {
          variance += Math.pow(score[i] - avg, 2);
        }
        variance /= n;
        
        stddev = Math.sqrt(variance);
        out.printf("%.5f\n", stddev);
      }
      
      
//      End solve()
    }
//    End Solution
}


  public static void main(String[] args) throws IOException {
    in = new InputReader(System.in);
    out = new PrintWriter(System.out);
    Solution solver = new Solution();
    solver.solve();
    out.close();
}


  static class InputReader {
    public BufferedReader br;
    public StringTokenizer st;

    public InputReader(InputStream stream) {
      br = new BufferedReader(new InputStreamReader(stream));
    }

    public int nextInt() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Integer.parseInt(st.nextToken());
    }

    public long nextLong() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Long.parseLong(st.nextToken());
    }

    public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return st.nextToken();
    }

    public double nextDouble() throws IOException {
      while (st == null || !st.hasMoreTokens()) {
        st = new StringTokenizer(br.readLine());
      }
      return Double.parseDouble(st.nextToken());
    }

  }

}