import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	}

	private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	}

	public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	}


}
 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	}

	private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	}

	public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	}


} Main public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	} main {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	} double dev = 0.0; dev 0.0 Scanner sc = new Scanner(System.in); sc new Scanner(System.in) do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true); true {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) {
				break;
			} n == 0 n 0 {
				break;
			} break; int[] grade = new int[n]; grade new int[n] n for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				grade[i] = sc.nextInt();
			} {
				grade[i] = sc.nextInt();
			} grade[i] = sc.nextInt() grade[i] grade i sc.nextInt() sc.nextInt sc dev = deviation(grade) dev deviation(grade) deviation grade System.out.println(dev) System.out.println System.out System System.out dev sc.close() sc.close sc String[] args args private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	} deviation {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	} double deviation = 0; deviation 0 for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		} int i = 0; int i = 0; i 0 i < grade.length i grade.length grade grade.length i++ i++ i {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		} {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		} deviation += Math.pow( grade[i] - average(grade) , 2) deviation Math.pow( grade[i] - average(grade) , 2) Math.pow Math grade[i] - average(grade) grade[i] grade i average(grade) average grade 2 deviation /= grade.length deviation grade.length grade grade.length deviation = Math.sqrt(deviation) deviation Math.sqrt(deviation) Math.sqrt Math deviation return deviation; deviation int[] grade grade public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	} average {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	} double average = 0; average 0 for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		} int i = 0; int i = 0; i 0 i < grade.length i grade.length grade grade.length i++ i++ i {
			average += grade[i];
		} {
			average += grade[i];
		} average += grade[i] average grade[i] grade i average /= grade.length average grade.length grade grade.length return average; average int[] grade grade public class Main {
	public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	}

	private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	}

	public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	}


} public class Main {
	public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	}

	private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	}

	public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	}


} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		double dev = 0.0;
		Scanner sc = new Scanner(System.in);

		do {
			int n = sc.nextInt();

			if (n == 0) {
				break;
			}

			int[] grade = new int[n];

			for (int i = 0; i < n; i++) {
				grade[i] = sc.nextInt();
			}

			dev = deviation(grade);

			System.out.println(dev);


		}while(true);

		sc.close();
	}

	private static double deviation(int[] grade) {
		double deviation = 0;

		for (int i = 0; i < grade.length; i++) {
			deviation += Math.pow( grade[i] - average(grade) , 2);
		}

		deviation /= grade.length;
		deviation = Math.sqrt(deviation);
		return deviation;
	}

	public static double average(int[] grade) {
		double average = 0;

		for (int i = 0; i < grade.length; i++) {
			average += grade[i];
		}

		average /= grade.length;

		return average;
	}


}

