import java.util.Scanner;
public class Main {
	private static Scanner sc=new Scanner(System.in);
	public static void main (String[] args){
	while(true){
		int n=sc.nextInt();
		if(n==0) break;
		int[] s=new int[n];
		double sum=0;
		for(int i=0;i<n;i++){
			s[i]=sc.nextInt();
			sum=sum+s[i];
		}
		double ave=sum/n;
		double ssum=0;
		for(int i=0;i<n;i++){
			ssum=ssum+(s[i]-ave)*(s[i]-ave);
		}
		System.out.println(Math.sqrt(ssum/n));
	}
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz