import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    }
} Main public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        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];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        } true {
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        } 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 double ave = 0.0; ave 0.0 for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            } int i = 0; int i = 0; i 0 i<n i n i++ i++ i {
                s[i] = sc.nextInt();
                ave += s[i];
            } {
                s[i] = sc.nextInt();
                ave += s[i];
            } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc ave += s[i] ave s[i] s i ave /= (double)n ave (double)n double v = 0; v 0 for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            } int i = 0; int i = 0; i 0 i<n i n i++ i++ i {
                v += (s[i] - ave)*(s[i] - ave);
            } {
                v += (s[i] - ave)*(s[i] - ave);
            } v += (s[i] - ave)*(s[i] - ave) v (s[i] - ave)*(s[i] - ave) (s[i] - ave) s[i] s i ave (s[i] - ave) s[i] s i ave double ans = Math.sqrt(v/(double)n); ans Math.sqrt(v/(double)n) Math.sqrt Math v/(double)n v (double)n System.out.printf("%f\n", ans) System.out.printf System.out System System.out "%f\n" ans sc.close() sc.close sc String[] args args public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    }
} public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int[] s = new int[n];
            double ave = 0.0;
            for(int i = 0; i<n; i++){
                s[i] = sc.nextInt();
                ave += s[i];
            }
            ave /= (double)n;
            double v = 0;
            for(int i = 0;i<n;i++){
                v += (s[i] - ave)*(s[i] - ave);
            }
            double ans = Math.sqrt(v/(double)n);
            System.out.printf("%f\n", ans);
        }
        sc.close();
    }
}
