import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	}
}



		

	 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	}
} Main public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	} main {
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) double[] array = new double[1000]; array new double[1000] 1000 int i; i for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		} ; {
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		} {
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		} double sum = 0; sum 0 double ave; ave double hen = 0; hen 0 double hen_sum = 0; hen_sum 0 int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if(n == 0)
				break; n == 0 n 0 break; for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			} i = 0; i = 0 i 0 i < n i n i++ i++ i {
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			} {
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			} double a = scan.nextDouble(); a scan.nextDouble() scan.nextDouble scan array[i] = a array[i] array i a sum += a sum a ave = sum / n ave sum / n sum n for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			} i = 0; i = 0 i 0 i < n i n i++ i++ i {
				hen += (ave - array[i]) * (ave - array[i]);
			} {
				hen += (ave - array[i]) * (ave - array[i]);
			} hen += (ave - array[i]) * (ave - array[i]) hen (ave - array[i]) * (ave - array[i]) (ave - array[i]) ave array[i] array i (ave - array[i]) ave array[i] array i double v = hen / n; v hen / n hen n double a = Math.sqrt(v); a Math.sqrt(v) Math.sqrt Math v System.out.println(a) System.out.println System.out System System.out a String[] args args public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	}
} public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	}
} Main
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(a);
		}
	}
}



		

	