import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	}
} Main public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	} main {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	} Scanner in = new Scanner(System.in); in new Scanner(System.in) while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		} true {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		} int n = in.nextInt(); n in.nextInt() in.nextInt in if(n==0) return; n==0 n 0 return; int sum = 0; sum 0 int[] darr = new int[n]; darr new int[n] n for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				darr[i] = in.nextInt();
				sum += darr[i];
			} {
				darr[i] = in.nextInt();
				sum += darr[i];
			} darr[i] = in.nextInt() darr[i] darr i in.nextInt() in.nextInt in sum += darr[i] sum darr[i] darr i double m = (double)sum / n; m (double)sum / n (double)sum n double bunsan = 0.0; bunsan 0.0 for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				bunsan += Math.pow(darr[i] - m, 2.0);
			} {
				bunsan += Math.pow(darr[i] - m, 2.0);
			} bunsan += Math.pow(darr[i] - m, 2.0) bunsan Math.pow(darr[i] - m, 2.0) Math.pow Math darr[i] - m darr[i] darr i m 2.0 bunsan /= n bunsan n System.out.println(Math.sqrt(bunsan)) System.out.println System.out System System.out Math.sqrt(bunsan) Math.sqrt Math bunsan String[] args args public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	}
} public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);

		while(true) {
			int n = in.nextInt();
			if(n==0) return;
			int sum = 0;
			int[] darr = new int[n];
			for (int i = 0; i < n; i++) {
				darr[i] = in.nextInt();
				sum += darr[i];
			}
			double m = (double)sum / n;
			double bunsan = 0.0;
			for(int i=0;i<n;i++) {
				bunsan += Math.pow(darr[i] - m, 2.0);
			}
			bunsan /= n;
			System.out.println(Math.sqrt(bunsan));
		}
	}
}