import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    } main {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    } Scanner sc=new Scanner(System.in); sc new Scanner(System.in) double m; m double v; v while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        } true {
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        } int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0) break; n==0 n 0 break; m=0 m 0 double s[]; s s=new double[n] s new double[n] n 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 v=0 v 0 for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            } int i=0; int i=0; i 0 i<n i n i++ i++ i {
                v+=(s[i]-m)*(s[i]-m);
            } {
                v+=(s[i]-m)*(s[i]-m);
            } v+=(s[i]-m)*(s[i]-m) v (s[i]-m)*(s[i]-m) (s[i]-m) s[i] s i m (s[i]-m) s[i] s i m v/=n v n System.out.println(Math.sqrt(v)) System.out.println System.out System System.out Math.sqrt(v) Math.sqrt Math v String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        double m;
        double v;
        while(true){
            int n=sc.nextInt();
            if(n==0) break;
            m=0;
            double s[];
            s=new double[n];
            for(int i=0;i<n;i++){
                s[i]=sc.nextDouble();
                m+=s[i];
            }
            m/=n;
            v=0;
            for(int i=0;i<n;i++){
                v+=(s[i]-m)*(s[i]-m);
            }
            v/=n;
            System.out.println(Math.sqrt(v));
        }
    }
} Main
import java.util.*;
import java.io.*;

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