import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

class Main {
	public static void main(String[] args) {
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util class Main {
	public static void main(String[] args) {
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
} Main public static void main(String[] args) {
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	} main {
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	} InputStreamReader isr = new InputStreamReader(System.in); isr new InputStreamReader(System.in) BufferedReader br = new BufferedReader(isr); br new BufferedReader(isr) try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} IOException e {
			e.printStackTrace();
		} e.printStackTrace() e.printStackTrace e {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} List<Double> ret = new ArrayList<Double>(); ret new ArrayList<Double>() do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true); true {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} int n = Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if (n == 0) {
					break;
				} n == 0 n 0 {
					break;
				} break; String[] s = br.readLine().split(" "); s br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " int i i num num sum = 0; sum 0 double ave; ave for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				} i = 0; i = 0 i 0 i < n i n i++ i++ i {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				} {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				} num = Integer.parseInt(s[i]) num Integer.parseInt(s[i]) Integer.parseInt Integer s[i] s i sum = sum + num sum sum + num sum num double hoge = 0.0; hoge 0.0 ave = (double) sum / n ave (double) sum / n (double) sum n for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				} i = 0; i = 0 i 0 i < n i n i++ i++ i {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				} {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				} num = Integer.parseInt(s[i]) num Integer.parseInt(s[i]) Integer.parseInt Integer s[i] s i hoge = hoge + Math.pow((num - ave), 2) hoge hoge + Math.pow((num - ave), 2) hoge Math.pow((num - ave), 2) Math.pow Math (num - ave) num ave 2 ret.add(Math.sqrt(hoge / n)) ret.add ret Math.sqrt(hoge / n) Math.sqrt Math hoge / n hoge n for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			} double d ret {
				System.out.println(String.format("%.8f", d));
			} {
				System.out.println(String.format("%.8f", d));
			} System.out.println(String.format("%.8f", d)) System.out.println System.out System System.out String.format("%.8f", d) String.format String "%.8f" d String[] args args
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

class Main {
	public static void main(String[] args) {
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		try {
			List<Double> ret = new ArrayList<Double>();
			do {
				int n = Integer.parseInt(br.readLine());
				if (n == 0) {
					break;
				}
				String[] s = br.readLine().split(" ");
				int i, num, sum = 0;
				double ave;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					sum = sum + num;
				}
				double hoge = 0.0;
				ave = (double) sum / n;
				for (i = 0; i < n; i++) {
					num = Integer.parseInt(s[i]);
					hoge = hoge + Math.pow((num - ave), 2);
				}
				ret.add(Math.sqrt(hoge / n));
			} while (true);
			for (double d : ret) {
				System.out.println(String.format("%.8f", d));
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}