import java.util.Scanner;

class Main{
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		int n;
		int[] s;
		int sum;
		double m;
		double a2;
		double a;

		while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		}
	}
} import java.util.Scanner; Scanner java.util class Main{
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		int n;
		int[] s;
		int sum;
		double m;
		double a2;
		double a;

		while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		}
	}
} Main public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		int n;
		int[] s;
		int sum;
		double m;
		double a2;
		double a;

		while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		}
	} main {
		Scanner sc = new Scanner(System.in);
		int n;
		int[] s;
		int sum;
		double m;
		double a2;
		double a;

		while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n int[] s; s int sum; sum double m; m double a2; a2 double a; a while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		} true {
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		} n = sc.nextInt() n sc.nextInt() sc.nextInt sc s = new int[n] s new int[n] n if(n == 0)
				break; n == 0 n 0 break; sum = 0 sum 0 m = 0 m 0 a = 0 a 0 a2 = 0 a2 0 for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				s[i] = sc.nextInt();
				sum += s[i];
			} {
				s[i] = sc.nextInt();
				sum += s[i];
			} s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc sum += s[i] sum s[i] s i m = (double)sum/n m (double)sum/n (double)sum n for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				a2 += Math.pow((s[i]-m),2.0);
			} {
				a2 += Math.pow((s[i]-m),2.0);
			} a2 += Math.pow((s[i]-m),2.0) a2 Math.pow((s[i]-m),2.0) Math.pow Math (s[i]-m) s[i] s i m 2.0 a2 = a2/n a2 a2/n a2 n a = Math.sqrt(a2) a Math.sqrt(a2) Math.sqrt Math a2 System.out.printf("%.8f\n",a) System.out.printf System.out System System.out "%.8f\n" a String args[] args
import java.util.Scanner;

class Main{
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		int n;
		int[] s;
		int sum;
		double m;
		double a2;
		double a;

		while(true){
			n = sc.nextInt();
			s = new int[n];
			if(n == 0)
				break;
			sum = 0;
			m = 0;
			a = 0;
			a2 = 0;
			for(int i=0; i<n; i++){
				s[i] = sc.nextInt();
				sum += s[i];
			}
			m = (double)sum/n;
			for(int i=0; i<n; i++){
				a2 += Math.pow((s[i]-m),2.0);
			}
			a2 = a2/n;
			a = Math.sqrt(a2);
			System.out.printf("%.8f\n",a);

		}
	}
}