import java.util.Scanner;

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

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


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

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


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

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		} true {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		} int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc if (N == 0) {
				break;
			} N == 0 N 0 {
				break;
			} break; int[] scores = new int[N]; scores new int[N] N int sum = 0; sum 0 for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} {
				scores[i] = sc.nextInt();
				sum += scores[i];
			} scores[i] = sc.nextInt() scores[i] scores i sc.nextInt() sc.nextInt sc sum += scores[i] sum scores[i] scores i double ave = sum * 1.0 / N; ave sum * 1.0 / N sum * 1.0 sum 1.0 N double bunsan = 0; bunsan 0 for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			} int score scores {
				bunsan += Math.pow( (score - ave) , 2);
			} {
				bunsan += Math.pow( (score - ave) , 2);
			} bunsan += Math.pow( (score - ave) , 2) bunsan Math.pow( (score - ave) , 2) Math.pow Math (score - ave) score ave 2 bunsan /= N bunsan N System.out.println(Math.sqrt(bunsan)) System.out.println System.out System System.out Math.sqrt(bunsan) Math.sqrt Math bunsan String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


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

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


	}
} Main
import java.util.Scanner;

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

		while (true) {
			int N = sc.nextInt();

			if (N == 0) {
				break;
			}

			int[] scores = new int[N];
			int sum = 0;
			for (int i = 0; i < N; i++) {
				scores[i] = sc.nextInt();
				sum += scores[i];
			}
			double ave = sum * 1.0 / N;
//			System.out.println(ave);

			double bunsan = 0;
			for (int score : scores) {
				bunsan += Math.pow( (score - ave) , 2);
			}
			bunsan /= N;

			System.out.println(Math.sqrt(bunsan));

		}


	}
}
