import java.io.InputStreamReader;
import java.io.LineNumberReader;

/**
 * http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_10_C
 * 
 * @author eitatsuro
 * 
 */
public class Main {
    public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
} import java.io.InputStreamReader; InputStreamReader java.io import java.io.LineNumberReader; LineNumberReader java.io public class Main {
    public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
} Main public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    } main {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    } try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        } Exception e {
            e.printStackTrace();
            System.exit(-1);
        } e.printStackTrace() e.printStackTrace e System.exit(-1) System.exit System -1 1 {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in)); lineNumReader new LineNumberReader(
                    new InputStreamReader(System.in)) String inputStr = null; inputStr null double  scores[] = null; scores null int studentsNum = 0; studentsNum 0 while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            } (inputStr = lineNumReader.readLine()) != null (inputStr = lineNumReader.readLine()) inputStr lineNumReader.readLine() lineNumReader.readLine lineNumReader null {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            } if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                } lineNumReader.getLineNumber()%2 == 1 lineNumReader.getLineNumber()%2 lineNumReader.getLineNumber() lineNumReader.getLineNumber lineNumReader 2 1 {
                    studentsNum = Integer.parseInt(inputStr);
                } studentsNum = Integer.parseInt(inputStr) studentsNum Integer.parseInt(inputStr) Integer.parseInt Integer inputStr if (studentsNum == 0) {
                    break;
                } studentsNum == 0 studentsNum 0 {
                    break;
                } break; if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                } lineNumReader.getLineNumber() % 2 == 0 lineNumReader.getLineNumber() % 2 lineNumReader.getLineNumber() lineNumReader.getLineNumber lineNumReader 2 0 {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                } String[] points = inputStr.split(" "); points inputStr.split(" ") inputStr.split inputStr " " scores = new double[studentsNum] scores new double[studentsNum] studentsNum int i = 0; i 0 for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    } String point points {
                        scores[i] = Long.parseLong(point);
                        i++;
                    } {
                        scores[i] = Long.parseLong(point);
                        i++;
                    } scores[i] = Long.parseLong(point) scores[i] scores i Long.parseLong(point) Long.parseLong Long point i++ i double sum = 0; sum 0 for (double score : scores) {
                        sum += score;
                    } double score scores {
                        sum += score;
                    } {
                        sum += score;
                    } sum += score sum score double mean = sum / studentsNum; mean sum / studentsNum sum studentsNum double sig2 = 0; sig2 0 for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    } double score scores {
                        sig2 += Math.pow(score - mean, 2);
                    } {
                        sig2 += Math.pow(score - mean, 2);
                    } sig2 += Math.pow(score - mean, 2) sig2 Math.pow(score - mean, 2) Math.pow Math score - mean score mean 2 double sigma = Math.sqrt(sig2 / studentsNum); sigma Math.sqrt(sig2 / studentsNum) Math.sqrt Math sig2 / studentsNum sig2 studentsNum System.out.println(String.format("%.8f", sigma)) System.out.println System.out System System.out String.format("%.8f", sigma) String.format String "%.8f" sigma lineNumReader.close() lineNumReader.close lineNumReader String[] args args public class Main {
    public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
} public class Main {
    public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
} Main
import java.io.InputStreamReader;
import java.io.LineNumberReader;

/**
 * http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_10_C
 * 
 * @author eitatsuro
 * 
 */
public class Main {
    public static void main(String[] args) {
        try {
            LineNumberReader lineNumReader = new LineNumberReader(
                    new InputStreamReader(System.in));
            
            String inputStr = null;
            double  scores[] = null;
            int studentsNum = 0;
            
            while ((inputStr = lineNumReader.readLine()) != null) {
                
                // ???????????°
                if (lineNumReader.getLineNumber()%2 == 1) {
                    studentsNum = Integer.parseInt(inputStr);
                }
                
                // ???????????¶.
                if (studentsNum == 0) {
                    break;
                }
                
                // ????????¢
                if (lineNumReader.getLineNumber() % 2 == 0) {
                    String[] points = inputStr.split(" ");
                    scores = new double[studentsNum];
                    int i = 0;
                    for (String point : points) {
                        scores[i] = Long.parseLong(point);
                        i++;
                    }
                    
                    // ?????????????¨????
                    double sum = 0;
                    for (double score : scores) {
                        sum += score;
                    }
                    double mean = sum / studentsNum;
                    
                    // ?????£ sig2
                    double sig2 = 0;
                    for (double score : scores) {
                        sig2 += Math.pow(score - mean, 2);
                    }
                    
                    // ?¨?????????? sigma
                    double sigma = Math.sqrt(sig2 / studentsNum);
                    
                    // ????????????.
                    System.out.println(String.format("%.8f", sigma));
                }
            }
            
            lineNumReader.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }
}