import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;



public class Main{
	public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	}

} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main{
	public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	}

} Main public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	} main {

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	} BufferedReader reader=new BufferedReader(new InputStreamReader(System.in)); reader new BufferedReader(new InputStreamReader(System.in)) int num; num int sum; sum double div div m; m String str; str String[] array_str; array_str try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		} catch(IOException e){
			System.out.print(e);
		} IOException e {
			System.out.print(e);
		} System.out.print(e) System.out.print System.out System System.out e {

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		} while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°????????? true {
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			} num=Integer.parseInt(reader.readLine()) num Integer.parseInt(reader.readLine()) Integer.parseInt Integer reader.readLine() reader.readLine reader if(num==0)break; num==0 num 0 break; sum=0 sum 0 div=0 div 0 str=reader.readLine() str reader.readLine() reader.readLine reader array_str=str.split(" ") array_str str.split(" ") str.split str " " for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			} int i=0; int i=0; i 0 i<num i num i++ i++ i {
				sum+=Integer.parseInt(array_str[i]);
			} {
				sum+=Integer.parseInt(array_str[i]);
			} sum+=Integer.parseInt(array_str[i]) sum Integer.parseInt(array_str[i]) Integer.parseInt Integer array_str[i] array_str i m=(double)sum/num m (double)sum/num (double)sum num for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			} int i=0; int i=0; i 0 i<num i num i++ i++ i {
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			} {
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			} div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num div (Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num (Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m) (Double.parseDouble(array_str[i])-m) Double.parseDouble(array_str[i]) Double.parseDouble Double array_str[i] array_str i m (Double.parseDouble(array_str[i])-m) Double.parseDouble(array_str[i]) Double.parseDouble Double array_str[i] array_str i m num System.out.printf("%.8f", Math.sqrt(div)) System.out.printf System.out System System.out "%.8f" Math.sqrt(div) Math.sqrt Math div System.out.println() System.out.println System.out System System.out String[] args args public class Main{
	public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	}

} public class Main{
	public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	}

} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;



public class Main{
	public static void main(String[] args){

		BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
		int num;
		int sum;
		double div, m;
		String str;
		String[] array_str;

		try{

			while(true){
			num=Integer.parseInt(reader.readLine());
			if(num==0)break;
			sum=0;
			div=0;//??????????????§?????????
			str=reader.readLine();
			array_str=str.split(" ");

			for(int i=0;i<num;i++){
				sum+=Integer.parseInt(array_str[i]);
			}
			m=(double)sum/num;//??????


			for(int i=0;i<num;i++){
				div+=(Double.parseDouble(array_str[i])-m)*(Double.parseDouble(array_str[i])-m)/num;
			}System.out.printf("%.8f", Math.sqrt(div));
			System.out.println();

			}//while???????????°?????????

		}catch(IOException e){
			System.out.print(e);
		}
	}

}