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

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader input = new BufferedReader(new InputStreamReader(System.in));

		while (true) {

			String first_line = input.readLine();

			// ????????°??¨?????°
			int student_num = Integer.parseInt(first_line);

			if (student_num == 0) {

				break;

			}

			// ????????\?????¨?????°
			String secound_lines = input.readLine();

			String[] score_arrays = secound_lines.split(" ");

			// ?????°???????¨???¨?????°
			double score_sum = 0;

			//n???????????????????????????????????°?????????
			for (int score_spot = 0; score_spot < score_arrays.length; score_spot++) {

				int score = Integer.parseInt(score_arrays[score_spot]);

				score_sum += score;

			}

			//???????????????
			double average = score_sum / student_num;

			//??°???a???2???
			double sequence_a_square = 0;

			//??°???a???2??????????????????
			for (int sequence_spot = 0; sequence_spot < score_arrays.length; sequence_spot++) {

				double score = Double.parseDouble(score_arrays[sequence_spot]);


				sequence_a_square += Math.pow(score - average, 2);

			}

			double distributed_a_square = sequence_a_square / student_num;

			//??°???a????????????
			double square_a = Math.sqrt(distributed_a_square);

			System.out.println(square_a);
		}

	}

}
/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