import java.util.Scanner;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int i, n;
		double s, sum, sum2;
		while(true){
			n = sc.nextInt();
			if(n==0) break;
			for(i=0, sum=0, sum2=0; i<n; i++){
				s = sc.nextDouble();
				sum += s;
				sum2 += s*s;
			}
			System.out.println(Math.sqrt(sum2/n-(sum/n)*(sum/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