import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

}
} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

}
} Main public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

} main {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

} try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	} {
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	} Scanner sc=new Scanner(System.in) Scanner sc=new Scanner(System.in) new Scanner(System.in) while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		} true {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		} int n=sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n==0) {break;} n==0 n 0 {break;} break; int score[]=new int[n]; score new int[n] n for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			} int i=0; int i=0; i 0 i<score.length i score.length score score.length i++ i++ i {
				score[i]=sc.nextInt();
			} {
				score[i]=sc.nextInt();
			} score[i]=sc.nextInt() score[i] score i sc.nextInt() sc.nextInt sc double average=0 average 0 variance=0; variance 0 for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			} int i=0; int i=0; i 0 i<score.length i score.length score score.length i++ i++ i {
				average=average+(double)score[i];
			} {
				average=average+(double)score[i];
			} average=average+(double)score[i] average average+(double)score[i] average (double)score[i] score i average=average/(double)score.length average average/(double)score.length average (double)score.length score score.length for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			} int i=0; int i=0; i 0 i<score.length i score.length score score.length i++ i++ i {
				variance=variance+Math.pow(score[i]-average,2.0);
			} {
				variance=variance+Math.pow(score[i]-average,2.0);
			} variance=variance+Math.pow(score[i]-average,2.0) variance variance+Math.pow(score[i]-average,2.0) variance Math.pow(score[i]-average,2.0) Math.pow Math score[i]-average score[i] score i average 2.0 variance=variance/(double)score.length variance variance/(double)score.length variance (double)score.length score score.length System.out.println(Math.sqrt(variance)) System.out.println System.out System System.out Math.sqrt(variance) Math.sqrt Math variance String[] args args public class Main {
	public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

}
} public class Main {
	public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try(Scanner sc=new Scanner(System.in)){
			while(true) {
				int n=sc.nextInt();
				if(n==0) {break;}
				int score[]=new int[n];
			for(int i=0;i<score.length;i++) {
				score[i]=sc.nextInt();
			}
			double average=0, variance=0;
			for(int i=0;i<score.length;i++) {
				average=average+(double)score[i];
			}
			average=average/(double)score.length;
			for(int i=0;i<score.length;i++) {
				variance=variance+Math.pow(score[i]-average,2.0);
			}
			variance=variance/(double)score.length;
			System.out.println(Math.sqrt(variance));
			
		}
	}
	

}
}
