import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		double[] array = new double[1000];
		int i;
		for(;;){
			double sum = 0;
			double ave;
			double hen = 0;
			double hen_sum = 0;
			int n = scan.nextInt();
			if(n == 0)
				break;
			for(i = 0; i < n; i++){
				double a = scan.nextDouble();
				array[i] = a;
				sum += a;
			}
			ave = sum / n;
			for(i = 0; i < n; i++){
				hen += (ave - array[i]) * (ave - array[i]);
			}
			double v = hen / n;
			double a = Math.sqrt(v);
			System.out.println(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