import java.util.*;
import java.lang.*;

/**
 * StandardDeviation
 */
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int n = sc.nextInt();

            if (n == 0)
                break;

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

            sum /= n;
            double ans = 0;
            for (int i = 0; i < n; i++) {
                ans += Math.pow((list[i] - sum), 2);
            }

            System.out.printf("%.8f\n", Math.sqrt((double) ans / 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