
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[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	}
}
 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[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	} main {
		Scanner sc = new Scanner(System.in);
		while (true) {
			int n = sc.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
			int n = sc.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		} true {
			int n = sc.nextInt();
			if (n == 0) break;
			int[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if (n == 0) break; n == 0 n 0 break; int[] s = new int[n]; s new int[n] n double e = 0.0 e 0.0 v = 0.0; v 0.0 for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			} {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			} s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc e += s[i] e s[i] s i v += s[i] * s[i] v s[i] * s[i] s[i] s i s[i] s i e /= n e n v = v / n - e * e v v / n - e * e v / n v n e * e e e System.out.println(Math.sqrt(v)) System.out.println System.out System System.out Math.sqrt(v) Math.sqrt Math v 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[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	}
} 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[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	}
} 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[] s = new int[n];
			double e = 0.0, v = 0.0;
			for (int i = 0; i < n; i++) {
				s[i] = sc.nextInt();
				e += s[i];
				v += s[i] * s[i];
			}
			e /= n;
			v = v / n - e * e;
			System.out.println(Math.sqrt(v));
		}
	}
}

