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

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

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	}
} import java.math.BigDecimal; BigDecimal java.math 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[] arges) {

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	}
} Main public static void main(String[] arges) {

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	} main {

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) List<Integer> klist = new ArrayList<Integer>(); klist new ArrayList<Integer>() List<String> vlist = new ArrayList<String>(); vlist new ArrayList<String>() int count = 1; count 1 while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		} true {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		} String line = sc.nextLine(); line sc.nextLine() sc.nextLine sc if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			} count % 2 != 0 count % 2 count 2 0 {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} klist.add(Integer.parseInt(line)) klist.add klist Integer.parseInt(line) Integer.parseInt Integer line if (line.equals("0")) {
					break;
				} line.equals("0") line.equals line "0" {
					break;
				} break; {
				vlist.add(line);
			} vlist.add(line) vlist.add vlist line count++ count int i = 0; i 0 for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		} Integer in klist {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		} {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		} if (in == 0) {
				break;
			} in == 0 in 0 {
				break;
			} break; Double[] on = new Double[in]; on new Double[in] in String vlistst = vlist.get(i); vlistst vlist.get(i) vlist.get vlist i String[] hu = vlistst.split(" "); hu vlistst.split(" ") vlistst.split vlistst " " for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			} int j = 0; int j = 0; j 0 j < on.length j on.length on on.length j++ j++ j {
				on[j] = Double.parseDouble(hu[j]);
			} {
				on[j] = Double.parseDouble(hu[j]);
			} on[j] = Double.parseDouble(hu[j]) on[j] on j Double.parseDouble(hu[j]) Double.parseDouble Double hu[j] hu j Double ave = 0.0; ave 0.0 for (int j = 0; j < on.length; j++) {
				ave += on[j];
			} int j = 0; int j = 0; j 0 j < on.length j on.length on on.length j++ j++ j {
				ave += on[j];
			} {
				ave += on[j];
			} ave += on[j] ave on[j] on j ave = ave / in ave ave / in ave in for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			} int j = 0; int j = 0; j 0 j < on.length j on.length on on.length j++ j++ j {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			} {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			} on[j] -=  ave on[j] on j ave on[j] = Math.pow(on[j], 2) on[j] on j Math.pow(on[j], 2) Math.pow Math on[j] on j 2 Double sum = 0.0; sum 0.0 for (int j = 0; j < on.length; j++) {
				sum += on[j];
			} int j = 0; int j = 0; j 0 j < on.length j on.length on on.length j++ j++ j {
				sum += on[j];
			} {
				sum += on[j];
			} sum += on[j] sum on[j] on j BigDecimal big = new BigDecimal(Math.sqrt(sum / in)); big new BigDecimal(Math.sqrt(sum / in)) big.setScale(6, BigDecimal.ROUND_DOWN) big.setScale big 6 BigDecimal.ROUND_DOWN BigDecimal BigDecimal.ROUND_DOWN System.out.println(big) System.out.println System.out System System.out big i++ i String[] arges arges public class Main {
	public static void main(String[] arges) {

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

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

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	}
} Main
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

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

		Scanner sc = new Scanner(System.in);
		List<Integer> klist = new ArrayList<Integer>();
		List<String> vlist = new ArrayList<String>();
		int count = 1;
		while (true) {
			
			String line = sc.nextLine();

			if (count % 2 != 0) {
				klist.add(Integer.parseInt(line));
				if (line.equals("0")) {
					break;
				}
			} else {
				vlist.add(line);
			}
			count++;
		}
		int i = 0;
		for (Integer in : klist) {
			if (in == 0) {
				break;
			}

			Double[] on = new Double[in];
			String vlistst = vlist.get(i);
			String[] hu = vlistst.split(" ");
			for (int j = 0; j < on.length; j++) {
				on[j] = Double.parseDouble(hu[j]);
			}
			Double ave = 0.0;
			for (int j = 0; j < on.length; j++) {
				ave += on[j];
			}
			ave = ave / in;
			for (int j = 0; j < on.length; j++) {
				on[j] -=  ave;
				on[j] = Math.pow(on[j], 2);
			}
			Double sum = 0.0;
			for (int j = 0; j < on.length; j++) {
				sum += on[j];
			}
			BigDecimal big = new BigDecimal(Math.sqrt(sum / in));
			big.setScale(6, BigDecimal.ROUND_DOWN);
			System.out.println(big);
			i++;
		}

	}
}