import java.util.*;

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

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	}
} import java.util.*; util.* java class Main {
	public static void main(String[] args) {

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	}
} Main public static void main(String[] args) {

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	} main {

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		} true {
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		} int n = stdIn.nextInt(); n stdIn.nextInt() stdIn.nextInt stdIn if(n == 0)
				break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n double sum = 0; sum 0 for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sum += s[i] = stdIn.nextInt();
			} {
				sum += s[i] = stdIn.nextInt();
			} sum += s[i] = stdIn.nextInt() sum s[i] = stdIn.nextInt() s[i] s i stdIn.nextInt() stdIn.nextInt stdIn double m = sum/n; m sum/n sum n sum = 0 sum 0 for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				sum += Math.pow(s[i]-m,2);
			} {
				sum += Math.pow(s[i]-m,2);
			} sum += Math.pow(s[i]-m,2) sum Math.pow(s[i]-m,2) Math.pow Math s[i]-m s[i] s i m 2 System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5)) System.out.printf System.out System System.out "%.5f\n" Math.pow((double)sum/n,0.5) Math.pow Math (double)sum/n (double)sum n 0.5 String[] args args
import java.util.*;

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

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	}
}