import static java.lang.Double.*;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	}

} import static java.lang.Double.*; import static java.lang.Double.*; import static java.lang.Double.*; import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	}

} Main public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	} main {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) StringBuilder sb = new StringBuilder(); sb new StringBuilder() int n = 0; n 0 while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		} ( n = sc.nextInt() ) != 0 ( n = sc.nextInt() ) n sc.nextInt() sc.nextInt sc 0 {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		} sc.nextLine() sc.nextLine sc String[] data = sc.nextLine().split(" "); data sc.nextLine().split(" ") sc.nextLine().split sc.nextLine() sc.nextLine sc " " double m = 0; m 0 for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				m += Double.parseDouble(data[i]);
			} {
				m += Double.parseDouble(data[i]);
			} m += Double.parseDouble(data[i]) m Double.parseDouble(data[i]) Double.parseDouble Double data[i] data i m = m / n m m / n m n double aa = 0; aa 0 for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			} {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			} double sm = parseDouble(data[i]) - m; sm parseDouble(data[i]) - m parseDouble(data[i]) parseDouble data[i] data i m aa += sm*sm aa sm*sm sm sm aa = aa / n aa aa / n aa n double a = Math.sqrt(aa); a Math.sqrt(aa) Math.sqrt Math aa sb.append(a + "\n") sb.append sb a + "\n" a "\n" System.out.print(sb) System.out.print System.out System System.out sb String[] args args public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	}

} public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	}

} Main
import static java.lang.Double.*;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();

		int n = 0;
		while (  ( n = sc.nextInt() ) != 0 ) {
			sc.nextLine();

			String[] data = sc.nextLine().split(" ");

			double m = 0;
			for (int i = 0; i < n; i++) {
				m += Double.parseDouble(data[i]);
			}
			m = m / n;

			double aa = 0;
			for (int i = 0; i < n; i++) {
				double sm = parseDouble(data[i]) - m;
				aa += sm*sm;
			}
			aa = aa / n;

			double a = Math.sqrt(aa);

			sb.append(a + "\n");
		}

		System.out.print(sb);
	}

}