import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    }
} Main public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    } main {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        } true {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        } int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if (n == 0) break; n == 0 n 0 break; double sum = 0 sum 0 sumX = 0 sumX 0 m; m double[] s = new double[n]; s new double[n] n for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                s[i] = scan.nextDouble();
                sum += s[i];
            } {
                s[i] = scan.nextDouble();
                sum += s[i];
            } s[i] = scan.nextDouble() s[i] s i scan.nextDouble() scan.nextDouble scan sum += s[i] sum s[i] s i m = sum / n m sum / n sum n for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                sumX += Math.pow((s[i] - m), 2) / n;
            } {
                sumX += Math.pow((s[i] - m), 2) / n;
            } sumX += Math.pow((s[i] - m), 2) / n sumX Math.pow((s[i] - m), 2) / n Math.pow((s[i] - m), 2) Math.pow Math (s[i] - m) s[i] s i m 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 public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    }
} public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        while (true) {
            int n = scan.nextInt();
            if (n == 0) break;

            double sum = 0, sumX = 0, m;
            double[] s = new double[n];

            for (int i = 0; i < n; i++) {
                s[i] = scan.nextDouble();
                sum += s[i];
            }

            m = sum / n;

            for (int i = 0; i < n; i++) {
                sumX += Math.pow((s[i] - m), 2) / n;
            }
            System.out.println(Math.sqrt(sumX));
        }
    }
}