import java.io.IOException;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) throws Exception {
		// TODO ?????????????????????????????????????????????
			Scanner sc = new Scanner(System.in);
			int a = sc.nextInt();
			double s = 0;
			double d = 0;
			while(a != 0){
				int c[] = new int[a];
				for(int b=0;b<a;++b){
					c[b]=sc.nextInt();
					s += c[b];
				}
				s = s/a;
				for(int b=0;b<a;++b){
					d += Math.pow(s-c[b], 2);
				}
				d=Math.sqrt(d/a);
				System.out.println(d);
				d=0;
				s=0;
				a = sc.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