import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double a = 0.0;

        while (true) {
            int n = scan.nextInt();
            int sum = 0;
            int[] students = new int[n];
            if (n == 0) break;

            for (int i = 0; i < n; i++) {
                int s = scan.nextInt();
                students[i] = s;
                sum += s;
            }
            double m = (double)sum / n;
            double sum2 = 0.0;
            for (int i = 0; i < n; i++) {
                sum2 += Math.pow(students[i] - m, 2);
            }
            a = Math.sqrt(sum2 / n);
            System.out.println(a);
        }
    }
}
/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