import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
} Main public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	} main {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	} try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		} Exception e {
			e.printStackTrace();
		} e.printStackTrace() e.printStackTrace e {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); input new BufferedReader(new InputStreamReader(System.in)) StringBuilder answer = new StringBuilder(); answer new StringBuilder() String lb = System.getProperty("line.separator"); lb System.getProperty("line.separator") System.getProperty System "line.separator" while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			} true {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			} final int n = Integer.parseInt(input.readLine()); n Integer.parseInt(input.readLine()) Integer.parseInt Integer input.readLine() input.readLine input if (n == 0) {
					break;
				} n == 0 n 0 {
					break;
				} break; final String[] line = input.readLine().split(" "); line input.readLine().split(" ") input.readLine().split input.readLine() input.readLine input " " int[] scores = new int[n]; scores new int[n] n double average = 0; average 0 for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				} {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				} scores[i] = Integer.parseInt(line[i]) scores[i] scores i Integer.parseInt(line[i]) Integer.parseInt Integer line[i] line i average += scores[i] average scores[i] scores i average /= n average n double deviation = 0; deviation 0 for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
					deviation += Math.pow(scores[i] - average, 2);
				} {
					deviation += Math.pow(scores[i] - average, 2);
				} deviation += Math.pow(scores[i] - average, 2) deviation Math.pow(scores[i] - average, 2) Math.pow Math scores[i] - average scores[i] scores i average 2 deviation = Math.pow(deviation / n, 0.5) deviation Math.pow(deviation / n, 0.5) Math.pow Math deviation / n deviation n 0.5 answer.append(String.valueOf(deviation)).append(lb) answer.append(String.valueOf(deviation)).append answer.append(String.valueOf(deviation)) answer.append answer String.valueOf(deviation) String.valueOf String deviation lb input.close() input.close input System.out.print(answer.toString()) System.out.print System.out System System.out answer.toString() answer.toString answer String[] args args public class Main {
	public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
} public class Main {
	public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
} Main
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) {
		try {
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			StringBuilder answer = new StringBuilder();
			String lb = System.getProperty("line.separator");
			
			while (true) {
				final int n = Integer.parseInt(input.readLine());
				if (n == 0) {
					break;
				}
				
				final String[] line = input.readLine().split(" ");
				int[] scores = new int[n];
				double average = 0;
				for (int i = 0; i < n; i++) {
					scores[i] = Integer.parseInt(line[i]);
					average += scores[i];
				}
				average /= n;

				double deviation = 0;
				for (int i = 0; i < n; i++) {
					deviation += Math.pow(scores[i] - average, 2);
				}
				deviation = Math.pow(deviation / n, 0.5);
				answer.append(String.valueOf(deviation)).append(lb);
			}
			input.close();
			
			System.out.print(answer.toString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}