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[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	}
} 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[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);

		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			int[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	} main {
		Scanner sc = new Scanner(System.in);

		while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			int[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while(true){
			int n = sc.nextInt();
			if(n == 0) break;
			int[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		} true {
			int n = sc.nextInt();
			if(n == 0) break;
			int[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		} int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n == 0) break; n == 0 n 0 break; int[] scores = new int[n]; scores new int[n] n int sum = 0; sum 0 for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			} {
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			} scores[i] = sc.nextInt() scores[i] scores i sc.nextInt() sc.nextInt sc sum += scores[i] sum scores[i] scores i double ave = (double) sum / n; ave (double) sum / n (double) sum n double a2 = 0; a2 0 for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
				a2 += (scores[i] - ave) * (scores[i] - ave);
			} {
				a2 += (scores[i] - ave) * (scores[i] - ave);
			} a2 += (scores[i] - ave) * (scores[i] - ave) a2 (scores[i] - ave) * (scores[i] - ave) (scores[i] - ave) scores[i] scores i ave (scores[i] - ave) scores[i] scores i ave a2 /= n a2 n double a = Math.sqrt(a2); a Math.sqrt(a2) Math.sqrt Math a2 System.out.printf("%.8f\n", a) System.out.printf System.out System System.out "%.8f\n" a 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[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	}
} 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[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	}
} 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[] scores = new int[n];

			int sum = 0;
			for(int i = 0;i < n;i++){
				scores[i] = sc.nextInt();
				//System.out.print(i + " : ");
				//System.out.println(scores[i]);
				sum += scores[i];
			}

			double ave = (double) sum / n;
			//System.out.println("ave : " + ave);

			double a2 = 0;
			for(int i = 0;i < n;i++){
				a2 += (scores[i] - ave) * (scores[i] - ave);
			}
			a2 /= n;
			double a = Math.sqrt(a2);

			System.out.printf("%.8f\n", a);
		}
		//System.out.println();
	}
}
