import java.util.Scanner;

public class Main {
	public static void main(String[] args)
	{
		Scanner scan = new Scanner(System.in);
		int count = scan.nextInt();
		double average;
		
		while(count != 0)
		{
			double[] score = new double[count + 1];
			
			for(int i = 0;i < count;i++)
			{
				score[i] = scan.nextDouble();
				score[count] += score[i];
			}
			average = score[count] / count;
			score[count] = 0;
			for(int i = 0;i < count;i++)
			{
				score[i] -= average;
				score[i] = Math.pow(score[i], 2);
				score[count] += score[i];
			}
			score[count] /= count;
			System.out.println(Math.sqrt(score[count]));
			count = scan.nextInt();
		}
	}
}
/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