import java.util.Scanner;

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

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