import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        while (a !=0) {
            double[] b = new double[a];
            for (int x = 0; x < a; x++) {
                b[x] = scan.nextInt();
            }
            double average = 0;
            for (int x = 0; x < a; x++) {
                average = average +b[x];
            }
            average = average / a;
            double var = 0;
            for (int x = 0; x < a; x++) {
                var = var +  ((b[x] - average) *(b[x] - average));
            }
            var = var /a;
            System.out.printf("%.8f\n",Math.sqrt(var));
            a = scan.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