import java.io.*;
 
public class Main {
 
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
        while(true){
            int n;
            if((n = Integer.parseInt(br.readLine())) == 0)
                break;
 
            String[] pointsStr = br.readLine().split(" ");
            int[] points = new int[n];
            for(int i = 0;i < n;i++){
                points[i] = Integer.parseInt(pointsStr[i]);
            }
 
            int sum = 0;
            for(int point : points){
                sum += point;
            }
            double mean = (new Double(sum)) / n;
            double disp = 0;
            for(int point : points){
                disp += (point - mean) * (point - mean);
            }
            disp /= n;
            System.out.printf("%.8f%n", Math.sqrt(disp));
        }
    }
 
}
/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