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

        java.util.Scanner sc = new java.util.Scanner(System.in);

        while (true) {
            int n = sc.nextInt();
            if (n == 0) { break; }

            int[] s = new int[n];
            double m = 0;
            for (int i = 0; i < n; i ++) {
                s[i] = sc.nextInt();
                m += s[i];
            }
            m /= n;

            double a = 0;
            for (int i = 0; i < n; i ++) { a += (s[i] - m) * (s[i] - m); }
            a = Math.sqrt(a / n);
            System.out.println(String.format("%10.8f", 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