import java.util.Scanner;

public class Main {
	void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
} import java.util.Scanner; Scanner java.util public class Main {
	void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
} Main void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	} run {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		} true {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		} int n = scan.nextInt(); n scan.nextInt() scan.nextInt scan if (n == 0) break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n double m = 0; m 0 double a = 0; a 0 for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = scan.nextInt();
				m += s[i];
			} {
				s[i] = scan.nextInt();
				m += s[i];
			} s[i] = scan.nextInt() s[i] s i scan.nextInt() scan.nextInt scan m += s[i] m s[i] s i m = m/n m m/n m n for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				a += (s[i] - m) * (s[i] - m);
			} {
				a += (s[i] - m) * (s[i] - m);
			} a += (s[i] - m) * (s[i] - m) a (s[i] - m) * (s[i] - m) (s[i] - m) s[i] s i m (s[i] - m) s[i] s i m System.out.println(Math.sqrt(a/n)) System.out.println System.out System System.out Math.sqrt(a/n) Math.sqrt Math a/n a n public static void main(String[] args) {
		new Main().run();
	} main {
		new Main().run();
	} new Main().run() new Main().run new Main() String[] args args public class Main {
	void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
} public class Main {
	void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
} Main
import java.util.Scanner;

public class Main {
	void run() {
		Scanner scan = new Scanner(System.in);
		while (true) {
			int n = scan.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double m = 0;
			double a = 0;
			for (int i = 0; i < n; i++) {
				s[i] = scan.nextInt();
				m += s[i];
			}
			m = m/n;
			for (int i = 0; i < n; i++) {
				a += (s[i] - m) * (s[i] - m);
			}
			System.out.println(Math.sqrt(a/n));
		}
	}
	public static void main(String[] args) {
		new Main().run();
	}
}