import java.util.Scanner;

public class Main {
	public static Scanner sc;
	public static void main(String[] args){
		sc=new Scanner(System.in);
		while(true){
			Double n=sc.nextDouble(),hou=(double) 0,sum=(double) 0;
			if(n==0)break;
			for(int i=0;i<n;i++){
				Double s=sc.nextDouble();
				hou+=s*s;
				sum+=s;
			}
			Double kin=sum/n;
			Double a=Math.sqrt((hou/n)-kin*kin);
			System.out.println(a);
		}
	}

}
/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