import java.util.*;
 
class Main{
    public static void main(String[] args){
		int n;
		double avr = 0.0;
		double ans = 0.0;
		Scanner scan = new Scanner(System.in);
		while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		}
    }
} import java.util.*; util.* java class Main{
    public static void main(String[] args){
		int n;
		double avr = 0.0;
		double ans = 0.0;
		Scanner scan = new Scanner(System.in);
		while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		}
    }
} Main public static void main(String[] args){
		int n;
		double avr = 0.0;
		double ans = 0.0;
		Scanner scan = new Scanner(System.in);
		while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		}
    } main {
		int n;
		double avr = 0.0;
		double ans = 0.0;
		Scanner scan = new Scanner(System.in);
		while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		}
    } int n; n double avr = 0.0; avr 0.0 double ans = 0.0; ans 0.0 Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		} (n = scan.nextInt()) != 0 (n = scan.nextInt()) n scan.nextInt() scan.nextInt scan 0 {
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		} int[] arr = new int[n]; arr new int[n] n int sum1 = 0; sum1 0 avr = 0.0 avr 0.0 for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			} {
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			} int tmp = scan.nextInt(); tmp scan.nextInt() scan.nextInt scan arr[i] = tmp arr[i] arr i tmp sum1 += tmp sum1 tmp avr = (double)sum1 / n avr (double)sum1 / n (double)sum1 n double sum2 = 0.0; sum2 0.0 for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			} {
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			} sum2 += (arr[i] - avr) * (arr[i] - avr) sum2 (arr[i] - avr) * (arr[i] - avr) (arr[i] - avr) arr[i] arr i avr (arr[i] - avr) arr[i] arr i avr ans = Math.sqrt(sum2 / n) ans Math.sqrt(sum2 / n) Math.sqrt Math sum2 / n sum2 n System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.*;
 
class Main{
    public static void main(String[] args){
		int n;
		double avr = 0.0;
		double ans = 0.0;
		Scanner scan = new Scanner(System.in);
		while((n = scan.nextInt()) != 0){
			int[] arr = new int[n];
			int sum1 = 0;
			avr = 0.0;
			for(int i=0; i<n; i++){
				int tmp = scan.nextInt();
				arr[i] = tmp;
				sum1 += tmp;
			}
			avr = (double)sum1 / n;
			double sum2 = 0.0;
			for(int i=0; i<n; i++){
				sum2 += (arr[i] - avr) * (arr[i] - avr);
			}
			ans = Math.sqrt(sum2 / n);
			System.out.println(ans);
		}
    }
}