
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	}
} Main public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	} main {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	} Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		} true {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		} int a = scanner.nextInt(); a scanner.nextInt() scanner.nextInt scanner if (a == 0)
				break; a == 0 a 0 break; double sum = 0; sum 0 int[] b = new int[a]; b new int[a] a for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			} int i = 0; int i = 0; i 0 i < a i a i++ i++ i {
				b[i] = scanner.nextInt();
				sum += b[i];
			} {
				b[i] = scanner.nextInt();
				sum += b[i];
			} b[i] = scanner.nextInt() b[i] b i scanner.nextInt() scanner.nextInt scanner sum += b[i] sum b[i] b i double m = sum / a; m sum / a sum a double aa = 0; aa 0 for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			} int i = 0; int i = 0; i 0 i < a i a i++ i++ i {
				aa += Math.pow(b[i] - m, 2) / a;
			} {
				aa += Math.pow(b[i] - m, 2) / a;
			} aa += Math.pow(b[i] - m, 2) / a aa Math.pow(b[i] - m, 2) / a Math.pow(b[i] - m, 2) Math.pow Math b[i] - m b[i] b i m 2 a System.out.println(Math.sqrt(aa)) System.out.println System.out System System.out Math.sqrt(aa) Math.sqrt Math aa String[] args args public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	}
} public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	}
} Main

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		while (true) {
			int a = scanner.nextInt();
			if (a == 0)
				break;
			double sum = 0;
			int[] b = new int[a];
			for (int i = 0; i < a; i++) {
				b[i] = scanner.nextInt();
				sum += b[i];
			}
			double m = sum / a;
			double aa = 0;
			for (int i = 0; i < a; i++) {
				aa += Math.pow(b[i] - m, 2) / a;
			}
			System.out.println(Math.sqrt(aa));

		}

	}
}