import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while (true) {
			String line = br.readLine();
			if ("0".equals(line))
				break;
			int n = Integer.parseInt(line);

			line = br.readLine();
			String[] scores = line.split(" ");
			double sum = 0;
			for (String score : scores) {
				sum += Integer.parseInt(score);
			}
			double avg = sum / n;

			sum = 0;
			for (String score : scores) {
				sum += Math.pow(Integer.parseInt(score) - avg, 2);
			}
			double a2 = sum / n;

			System.out.printf("%.5f%n", Math.sqrt(a2));
		}

		if (br != null) {
			br.close();
			br = null;
		}
	}
}
/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