import java.util.Scanner;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		}
	}
} import java.util.Scanner; Scanner java.util class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		}
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		}
	} main {
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int i i n; n double s s sum sum sum2; sum2 while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		} true {
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		} n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n==0) break; n==0 n 0 break; for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			} i=0, sum=0, sum2=0; i=0 i 0 sum=0 sum 0 sum2=0 sum2 0 i<n i n i++ i++ i {
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			} {
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			} s = sc.nextDouble() s sc.nextDouble() sc.nextDouble sc sum += s sum s sum2 += s*s sum2 s*s s s System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n))) System.out.println System.out System System.out Math.sqrt(sum2/n-(sum/n)*(sum/n)) Math.sqrt Math sum2/n-(sum/n)*(sum/n) sum2/n sum2 n (sum/n)*(sum/n) (sum/n) sum n (sum/n) sum n String[] args args
import java.util.Scanner;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/n)));
		}
	}
}