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

public class Main{

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	}

} import java.util.ArrayList; ArrayList java.util import java.util.Scanner; Scanner java.util public class Main{

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	}

} Main public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	} main {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) ArrayList<String[]> all = new ArrayList<String[]>(); all new ArrayList<String[]>() int count = 0; count 0 while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		} true {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		} String[] kari = new String[2]; kari new String[2] 2 kari[0] = sc.nextLine() kari[0] kari 0 sc.nextLine() sc.nextLine sc if (kari[0].equals("0")) {
				break;
			} kari[0].equals("0") kari[0].equals kari[0] kari 0 "0" {
				break;
			} break; kari[1] = sc.nextLine() kari[1] kari 1 sc.nextLine() sc.nextLine sc all.add(kari) all.add all kari count++ count for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		} int i = 0; int i = 0; i 0 i < count i count i++ i++ i {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		} {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		} String[] kari = all.get(i); kari all.get(i) all.get all i double n = Double.parseDouble(kari[0]); n Double.parseDouble(kari[0]) Double.parseDouble Double kari[0] kari 0 String[] stu = kari[1].split(" "); stu kari[1].split(" ") kari[1].split kari[1] kari 1 " " double[] student = new double[(int)n]; student new double[(int)n] (int)n double sum = 0; sum 0 for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			} int j = 0; int j = 0; j 0 j < n j n j++ j++ j {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			} {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			} student[j] = Double.parseDouble(stu[j]) student[j] student j Double.parseDouble(stu[j]) Double.parseDouble Double stu[j] stu j sum += student[j] sum student[j] student j double m = sum / n; m sum / n sum n double answer = 0; answer 0 for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			} int j = 0; int j = 0; j 0 j < n j n j++ j++ j {
				answer += (student[j] - m) * (student[j] - m);
			} {
				answer += (student[j] - m) * (student[j] - m);
			} answer += (student[j] - m) * (student[j] - m) answer (student[j] - m) * (student[j] - m) (student[j] - m) student[j] student j m (student[j] - m) student[j] student j m System.out.println(Math.sqrt(answer/n)) System.out.println System.out System System.out Math.sqrt(answer/n) Math.sqrt Math answer/n answer n String[] args args public class Main{

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	}

} public class Main{

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	}

} Main
import java.util.ArrayList;
import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);

		ArrayList<String[]> all = new ArrayList<String[]>();
		int count = 0;

		while (true) {
			String[] kari = new String[2];
			kari[0] = sc.nextLine();

			if (kari[0].equals("0")) {
				break;
			}

			kari[1] = sc.nextLine();

			all.add(kari);
			count++;
		}

		for (int i = 0; i < count; i++) {
			String[] kari = all.get(i);
			double n = Double.parseDouble(kari[0]);
			String[] stu = kari[1].split(" ");
			double[] student = new double[(int)n];
			double sum = 0;
			for (int j = 0; j < n; j++) {
				student[j] = Double.parseDouble(stu[j]);
				sum += student[j];
			}
			double m = sum / n;

			double answer = 0;
			for (int j = 0; j < n; j++) {
				answer += (student[j] - m) * (student[j] - m);
			}
			System.out.println(Math.sqrt(answer/n));
		}

	}

}