
import java.util.Scanner;

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

import java.util.Scanner;

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