
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	}

} import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.Scanner; Scanner java.util public class Main {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	}

} Main public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	} main {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) List<Double> list = new ArrayList<Double>(); list new ArrayList<Double>() while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		} true {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if (n == 0) {
				break;
			} n == 0 n 0 {
				break;
			} break; int[] s = new int[n]; s new int[n] n int sum = 0; sum 0 for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = scan.nextInt();
				sum += s[i];
			} {
				s[i] = scan.nextInt();
				sum += s[i];
			} s[i] = scan.nextInt() s[i] s i scan.nextInt() scan.nextInt scan sum += s[i] sum s[i] s i double m = (double)sum / n; m (double)sum / n (double)sum n double alpha = 0; alpha 0 for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				alpha += (s[i] - m) * (s[i] - m);
			} {
				alpha += (s[i] - m) * (s[i] - m);
			} alpha += (s[i] - m) * (s[i] - m) alpha (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m alpha = Math.sqrt(alpha / n) alpha Math.sqrt(alpha / n) Math.sqrt Math alpha / n alpha n list.add(alpha) list.add list alpha for (Double alpha : list) {
			System.out.println(alpha);
		} Double alpha list {
			System.out.println(alpha);
		} {
			System.out.println(alpha);
		} System.out.println(alpha) System.out.println System.out System System.out alpha scan.close() scan.close scan String[] args args public class Main {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	}

} public class Main {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	}

} Main

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		List<Double> list = new ArrayList<Double>();
		
		while (true) {
			int n = scan.nextInt();
			if (n == 0) {
				break;
			}

			int[] s = new int[n];
			int sum = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				sum += s[i];
			}
			double m = (double)sum / n;

			double alpha = 0;
			for (int i = 0; i < n; i++) {
				alpha += (s[i] - m) * (s[i] - m);
			}
			alpha = Math.sqrt(alpha / n);
			list.add(alpha);
		}

		for (Double alpha : list) {
			System.out.println(alpha);
		}
		
		scan.close();
	}

}