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));
		}
	}
} import java.io.*; io.* java 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));
		}
	}
} 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));
		}
	} main {
		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));
		}
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 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));
		} 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));
		} int n = Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br if(n == 0)break; n == 0 n 0 break; double m = 0 m 0 sig = 0; sig 0 String[] div = br.readLine().split(" "); div br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " for(int i=0; i<n; i++){
				double s = Double.parseDouble(div[i]);
				m += s;
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				double s = Double.parseDouble(div[i]);
				m += s;
			} {
				double s = Double.parseDouble(div[i]);
				m += s;
			} double s = Double.parseDouble(div[i]); s Double.parseDouble(div[i]) Double.parseDouble Double div[i] div i m += s m s m = m / n m m / n m n for(int i=0; i<n; i++){
				double s = Double.parseDouble(div[i]);
				sig +=(s-m)*(s-m);
			} int i=0; int i=0; i 0 i<n i n i++ i++ i {
				double s = Double.parseDouble(div[i]);
				sig +=(s-m)*(s-m);
			} {
				double s = Double.parseDouble(div[i]);
				sig +=(s-m)*(s-m);
			} double s = Double.parseDouble(div[i]); s Double.parseDouble(div[i]) Double.parseDouble Double div[i] div i sig +=(s-m)*(s-m) sig (s-m)*(s-m) (s-m) s m (s-m) s m System.out.println(Math.sqrt(sig/n)) System.out.println System.out System System.out Math.sqrt(sig/n) Math.sqrt Math sig/n sig n String[] arg arg
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));
		}
	}
}