import java.io.*;

class Main {
	public static void main(String[] arg)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			int n = Integer.parseInt(br.readLine());
			if(n == 0)break;
			double m = 0,sig = 0;
			String[] div = br.readLine().split(" ");
			for(int i=0; i<n; i++){
				double s = Double.parseDouble(div[i]);
				m += s;
			}
			m = m / n;
			for(int i=0; i<n; i++){
				double s = Double.parseDouble(div[i]);
				sig +=(s-m)*(s-m);
			}
			System.out.println(Math.sqrt(sig/n));
		}
	}
}
/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