import java.util.Scanner;

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

		Scanner scan = new Scanner(System.in);

		int n;
		while(true){
			n = scan.nextInt();
			if(n == 0)break;
			double sum = 0;
			double ave = 0;
			double var = 0;
		
			int a[];
			a = new int[n];
	
			for(int i = 0;i < n;i++){
				a[i] = scan.nextInt();
			}
		
			for(int i = 0; i < n; i++){
				sum += a[i];
			}
		
			ave = sum / n;
		
			for(int i = 0; i < n; i++){
				var += Math.pow((a[i] - ave),2);
			}
		
			System.out.println(Math.sqrt(var/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