import java.util.Scanner;

public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
} Main public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        } true {
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0) break; n==0 n 0 break; int s[] = new int[n]; s new int[n] n int sum = 0; sum 0 for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                s[i] = sc.nextInt();
                sum = sum+s[i];
            } {
                s[i] = sc.nextInt();
                sum = sum+s[i];
            } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc sum = sum+s[i] sum sum+s[i] sum s[i] s i double ave = (double)sum/n; ave (double)sum/n (double)sum n double a2 = 0; a2 0 for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            } {
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            } a2 = a2+(s[i]-ave)*(s[i]-ave) a2 a2+(s[i]-ave)*(s[i]-ave) a2 (s[i]-ave)*(s[i]-ave) (s[i]-ave) s[i] s i ave (s[i]-ave) s[i] s i ave a2 = a2/n a2 a2/n a2 n double a = Math.pow(a2, 0.5); a Math.pow(a2, 0.5) Math.pow Math a2 0.5 System.out.println(a) System.out.println System.out System System.out a sc.close() sc.close sc String[] arg arg public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
} public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
} Main
import java.util.Scanner;

public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
}
