import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
        int n;

        while(true){
            n = Integer.parseInt(br.readLine());
            if(n == 0){
                break;
            }

            String[] str = br.readLine().split(" ");
            double ave = 0;
            double alpha = 0;
            double[] line = new double[n];
            for(int i = 0; i < n; i++){
                line[i] = Double.parseDouble(str[i]);
                ave += line[i];
            }
            ave /= n;

            for(int i = 0; i < n; i++){
                alpha += Math.pow((line[i]-ave), 2);
            }
            alpha /= n;
            sb.append(Math.sqrt(alpha)).append("\n");
        }
        System.out.print(sb.toString());
    }
}
/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