import java.util.*;
import java.math.*;

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;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    }
} import java.util.*; util.* java import java.math.*; math.* 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;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(true) {
            int n = sc.nextInt();
            if(n == 0) break;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    } main {
        Scanner sc = new Scanner(System.in);
        while(true) {
            int n = sc.nextInt();
            if(n == 0) break;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true) {
            int n = sc.nextInt();
            if(n == 0) break;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        } true {
            int n = sc.nextInt();
            if(n == 0) break;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        } int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0) break; n == 0 n 0 break; double[] s = new double[n]; s new double[n] n double sum = 0.0; sum 0.0 for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                s[i] = sc.nextDouble();
                sum += s[i];
            } {
                s[i] = sc.nextDouble();
                sum += s[i];
            } s[i] = sc.nextDouble() s[i] s i sc.nextDouble() sc.nextDouble sc sum += s[i] sum s[i] s i double ave = sum / (double)n; ave sum / (double)n sum (double)n double ans = 0.0; ans 0.0 for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                ans += (s[i] - ave) * (s[i] - ave);
            } {
                ans += (s[i] - ave) * (s[i] - ave);
            } ans += (s[i] - ave) * (s[i] - ave) ans (s[i] - ave) * (s[i] - ave) (s[i] - ave) s[i] s i ave (s[i] - ave) s[i] s i ave ans = Math.sqrt(ans/(double)n) ans Math.sqrt(ans/(double)n) Math.sqrt Math ans/(double)n ans (double)n System.out.printf("%.8f\n", ans) System.out.printf System.out System System.out "%.8f\n" ans 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;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    }
} 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;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    }
} Main
import java.util.*;
import java.math.*;

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;
            double[] s = new double[n];
            double sum = 0.0;
            for(int i = 0; i < n; i++) {
                s[i] = sc.nextDouble();
                sum += s[i];
            }
            double ave = sum / (double)n;
            double ans = 0.0;
            for(int i = 0; i < n; i++) {
                ans += (s[i] - ave) * (s[i] - ave);
            }
            ans = Math.sqrt(ans/(double)n);
            System.out.printf("%.8f\n", ans);
        }
    }
}
