import java.lang.Math;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    }
} import java.lang.Math; Math java.lang import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    }
} Main public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    } main {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    } try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        } {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        } Scanner sc = new Scanner(System.in) Scanner sc = new Scanner(System.in) new Scanner(System.in) while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            } true {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) break; n == 0 n 0 break; double s[] = new double[n]; s new double[n] n double m = 0; m 0 for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                    s[i] = sc.nextDouble();
                    m += s[i];
                } {
                    s[i] = sc.nextDouble();
                    m += s[i];
                } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc m += s[i] m s[i] s i m /= n m n double v = 0; v 0 for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                } {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                } s[i] = Math.pow(s[i]-m, 2) s[i] s i Math.pow(s[i]-m, 2) Math.pow Math s[i]-m s[i] s i m 2 v += s[i] v s[i] s i v /= n v n double d = Math.pow(v, 0.5); d Math.pow(v, 0.5) Math.pow Math v 0.5 System.out.println(d) System.out.println System.out System System.out d String[] args args public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    }
} public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    }
} Main
import java.lang.Math;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        try (Scanner sc = new Scanner(System.in)) {
            while (true) {
                int n = sc.nextInt();
                if (n == 0) break;
                double s[] = new double[n];
                double m = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = sc.nextDouble();
                    m += s[i];
                }
                m /= n;
                double v = 0;
                for (int i = 0; i < n; i++) {
                    s[i] = Math.pow(s[i]-m, 2);
                    v += s[i];
                }
                v /= n;
                double d = Math.pow(v, 0.5);
                System.out.println(d);
            }
        }
    }
}
