import java.util.Scanner;
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;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    }

    public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    }

    public static double average(double[] s) {
        return sum(s) / (double)s.length;
    }

    public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    }
} import java.util.Scanner; Scanner 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;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    }

    public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    }

    public static double average(double[] s) {
        return sum(s) / (double)s.length;
    }

    public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int n = sc.nextInt();
            if (n == 0) {
                break;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int n = sc.nextInt();
            if (n == 0) {
                break;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
            int n = sc.nextInt();
            if (n == 0) {
                break;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        } true {
            int n = sc.nextInt();
            if (n == 0) {
                break;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) {
                break;
            } n == 0 n 0 {
                break;
            } break; double[] s = new double[n]; s new double[n] n for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            } int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
                s[i] = sc.nextDouble();
            } {
                s[i] = sc.nextDouble();
            } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc System.out.printf("%.8f\n",Math.sqrt(variance(s))) System.out.printf System.out System System.out "%.8f\n" Math.sqrt(variance(s)) Math.sqrt Math variance(s) variance s sc.close() sc.close sc String[] args args public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    } sum {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    } double sum = 0.0; sum 0.0 for (int i = 0; i < s.length; i++) {
            sum += s[i];
        } int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
            sum += s[i];
        } {
            sum += s[i];
        } sum += s[i] sum s[i] s i return sum; sum double[] s s public static double average(double[] s) {
        return sum(s) / (double)s.length;
    } average {
        return sum(s) / (double)s.length;
    } return sum(s) / (double)s.length; sum(s) / (double)s.length sum(s) sum s (double)s.length s s.length double[] s s public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    } variance {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    } double sum = 0; sum 0 for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        } int i = 0; int i = 0; i 0 i < s.length i s.length s s.length i++ i++ i {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        } {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        } sum += (s[i] - average(s)) * (s[i] - average(s)) sum (s[i] - average(s)) * (s[i] - average(s)) (s[i] - average(s)) s[i] s i average(s) average s (s[i] - average(s)) s[i] s i average(s) average s return sum / (double)s.length; sum / (double)s.length sum (double)s.length s s.length double[] s s 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;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    }

    public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    }

    public static double average(double[] s) {
        return sum(s) / (double)s.length;
    }

    public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    }
} 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;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    }

    public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    }

    public static double average(double[] s) {
        return sum(s) / (double)s.length;
    }

    public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    }
} Main
import java.util.Scanner;
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;
            }
            double[] s = new double[n];
            for (int i = 0; i < s.length; i++) {
                s[i] = sc.nextDouble();
            }
            System.out.printf("%.8f\n",Math.sqrt(variance(s)));
        }
        sc.close();
    }

    public static double sum(double[] s) {
        double sum = 0.0;
        for (int i = 0; i < s.length; i++) {
            sum += s[i];
        }
        return sum;
    }

    public static double average(double[] s) {
        return sum(s) / (double)s.length;
    }

    public static double variance(double[] s) {
        double sum = 0;
        for (int i = 0; i < s.length; i++) {
            sum += (s[i] - average(s)) * (s[i] - average(s));
        }
        return sum / (double)s.length;
    }
}
