import java.util.Scanner;

/**
 * @author kawakami
 *
 */
class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	}

} import java.util.Scanner; Scanner java.util class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	}

} Main /**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	} main {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	} Scanner as = new Scanner(System.in); as new Scanner(System.in) int num; num double hen = 0; hen 0 double sum = 0; sum 0 double hei = 0; hei 0 double ten[]; ten String str; str while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		} true {
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		} num = as.nextInt() num as.nextInt() as.nextInt as if(num == 0){
				
				break;
				
			} num == 0 num 0 {
				
				break;
				
			} break; ten = new double[num] ten new double[num] num for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			} int i=0; int i=0; i 0 i<num i num i++ i++ i {
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			} {
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			} ten[i] = as.nextDouble() ten[i] ten i as.nextDouble() as.nextDouble as hei = hei + ten[i] hei hei + ten[i] hei ten[i] ten i hei = hei / num hei hei / num hei num for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			} int i=0; int i=0; i 0 i<num i num i++ i++ i {
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			} {
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			} sum = sum + (ten[i]-hei)*(ten[i]-hei) sum sum + (ten[i]-hei)*(ten[i]-hei) sum (ten[i]-hei)*(ten[i]-hei) (ten[i]-hei) ten[i] ten i hei (ten[i]-hei) ten[i] ten i hei hen = Math.sqrt(sum/num) hen Math.sqrt(sum/num) Math.sqrt Math sum/num sum num str = String.valueOf(hen) str String.valueOf(hen) String.valueOf String hen System.out.println(str) System.out.println System.out System System.out str hei = 0 hei 0 sum = 0 sum 0 hen = 0 hen 0 String[] args args
import java.util.Scanner;

/**
 * @author kawakami
 *
 */
class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	}

}