import java.util.Scanner;

public class Main{
    public static void main(String[] arg){
        Scanner sc = new Scanner(System.in);
        while(true){
            int n = sc.nextInt();
            if(n==0) break;
            int s[] = new int[n];
            int sum = 0;
            for(int i=0;i<n;i++){
                s[i] = sc.nextInt();
                sum = sum+s[i];
            }
            double ave = (double)sum/n;
            double a2 = 0;
            for(int i=0;i<n;i++){
                a2 = a2+(s[i]-ave)*(s[i]-ave);
            }
            a2 = a2/n;
            double a = Math.pow(a2, 0.5);
            System.out.println(a);
        }
        sc.close();
    }
}

/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