import java.util.Scanner;

class Main{
 
	public static void main(String[] args) {

		int n,i;
		double ave,std;

		Scanner scan = new Scanner(System.in);
		
		while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		}
		
		scan.close();
	}
} import java.util.Scanner; Scanner java.util class Main{
 
	public static void main(String[] args) {

		int n,i;
		double ave,std;

		Scanner scan = new Scanner(System.in);
		
		while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		}
		
		scan.close();
	}
} Main public static void main(String[] args) {

		int n,i;
		double ave,std;

		Scanner scan = new Scanner(System.in);
		
		while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		}
		
		scan.close();
	} main {

		int n,i;
		double ave,std;

		Scanner scan = new Scanner(System.in);
		
		while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		}
		
		scan.close();
	} int n n i; i double ave ave std; std Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		} true {
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		} int sum=0; sum 0 double var=0; var 0 n = scan.nextInt() n scan.nextInt() scan.nextInt scan if(n==0) break; n==0 n 0 break; int a[] = new int[n]; a new int[n] n for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			} i=0; i=0 i 0 i<n i n i++ i++ i {
				a[i] = scan.nextInt();
				sum += a[i];
			} {
				a[i] = scan.nextInt();
				sum += a[i];
			} a[i] = scan.nextInt() a[i] a i scan.nextInt() scan.nextInt scan sum += a[i] sum a[i] a i ave = (double)sum/n ave (double)sum/n (double)sum n for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			} i=0; i=0 i 0 i<n i n i++ i++ i {
				var += ( (a[i] - ave)*(a[i] - ave) );
			} {
				var += ( (a[i] - ave)*(a[i] - ave) );
			} var += ( (a[i] - ave)*(a[i] - ave) ) var ( (a[i] - ave)*(a[i] - ave) ) (a[i] - ave) a[i] a i ave (a[i] - ave) a[i] a i ave std = Math.sqrt(var/n) std Math.sqrt(var/n) Math.sqrt Math var/n var n System.out.printf("%.5f\n",std) System.out.printf System.out System System.out "%.5f\n" std scan.close() scan.close scan String[] args args
import java.util.Scanner;

class Main{
 
	public static void main(String[] args) {

		int n,i;
		double ave,std;

		Scanner scan = new Scanner(System.in);
		
		while(true)
		{
			int sum=0;
			double var=0;
			
			n = scan.nextInt();
			
			if(n==0) break;
			
			int a[] = new int[n];
			
			for(i=0; i<n; i++)
			{
				a[i] = scan.nextInt();
				sum += a[i];
			}
			
			ave = (double)sum/n;
			
			for(i=0; i<n; i++)
			{
				var += ( (a[i] - ave)*(a[i] - ave) );
			}
			
			std = Math.sqrt(var/n);
			
			System.out.printf("%.5f\n",std);
		}
		
		scan.close();
	}
}