import java.util.*;

class Main {
	public static void main(String[] args) {

		Scanner stdIn = new Scanner(System.in);

		while(true){
			int n = stdIn.nextInt();
			if(n == 0)
				break;

			int[] s = new int[n];
			double sum = 0;

			for (int i=0; i<n; i++) {
				sum += s[i] = stdIn.nextInt();
			}

			double m = sum/n;
			sum = 0;

			for (int i=0; i<n; i++) {
				sum += Math.pow(s[i]-m,2);
			}
			System.out.printf("%.5f\n",Math.pow((double)sum/n,0.5));
		}
	}
}
/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