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

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

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    }
} import java.util.Scanner; Scanner java.util import java.lang.Math; Math java.lang public class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    }
} Main public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    } main {
        Scanner stdIn = new Scanner(System.in);

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    } Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    } true {
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    } int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn if(n==0) break; n==0 n 0 break; int a[] = new int[n]; a new int[n] n double sum = 0; sum 0 double sum1 = 0; sum1 0 double t = 0; t 0 for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            a[i] = stdIn.nextInt();
            sum += a[i];
        } {
            a[i] = stdIn.nextInt();
            sum += a[i];
        } a[i] = stdIn.nextInt() a[i] a i stdIn.nextInt() stdIn.nextInt stdIn sum += a[i] sum a[i] a i for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        } int j = 0; int j = 0; j 0 j < n j n j++ j++ j {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        } {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        } sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n) sum1 (double) (a[j] - sum / n) * (a[j] - sum / n) (double) (a[j] - sum / n) a[j] a j sum / n sum n (a[j] - sum / n) a[j] a j sum / n sum n t = Math.sqrt((double) sum1 / n) t Math.sqrt((double) sum1 / n) Math.sqrt Math (double) sum1 / n (double) sum1 n System.out.println(t) System.out.println System.out System System.out t String[] args args public class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    }
} public class Main {
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    }
} Main
import java.util.Scanner;
import java.lang.Math;

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

        while(true){
        int n = stdIn.nextInt();
        if(n==0) break;
        int a[] = new int[n];
        double sum = 0;
        double sum1 = 0;
        double t = 0;

        for (int i = 0; i < n; i++) {
            a[i] = stdIn.nextInt();
            sum += a[i];
        }

        for (int j = 0; j < n; j++) {
            sum1 += (double) (a[j] - sum / n) * (a[j] - sum / n);
        }

        t = Math.sqrt((double) sum1 / n);

        System.out.println(t);
    }
    }
}
