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

public class Main {
	public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io public class Main {
	public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	}
} Main public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	} main {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	} BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringBuffer sb = new StringBuffer(); sb new StringBuffer() while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		} true {
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		} int n = Integer.parseInt(br.readLine()); n Integer.parseInt(br.readLine()) Integer.parseInt Integer br.readLine() br.readLine br int i = 0; i 0 double m = 0; m 0 double a = 0; a 0 if( n==0 ) break; n==0 n 0 break; String[] s = br.readLine().split(" "); s br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			} i=0 ; i=0 i 0 i<n i n i++ i++ i {
				m = m+Double.parseDouble(s[i]);
			} {
				m = m+Double.parseDouble(s[i]);
			} m = m+Double.parseDouble(s[i]) m m+Double.parseDouble(s[i]) m Double.parseDouble(s[i]) Double.parseDouble Double s[i] s i m = m/n m m/n m n for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			} i=0 ; i=0 i 0 i<n i n i++ i++ i {
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			} {
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			} a = a+Math.pow(Double.parseDouble(s[i])-m, 2) a a+Math.pow(Double.parseDouble(s[i])-m, 2) a Math.pow(Double.parseDouble(s[i])-m, 2) Math.pow Math Double.parseDouble(s[i])-m Double.parseDouble(s[i]) Double.parseDouble Double s[i] s i m 2 a = Math.sqrt(a/n) a Math.sqrt(a/n) Math.sqrt Math a/n a n sb.append(String.format("%.6f", a)).append("\n") sb.append(String.format("%.6f", a)).append sb.append(String.format("%.6f", a)) sb.append sb String.format("%.6f", a) String.format String "%.6f" a "\n" System.out.print(sb) System.out.print System.out System System.out sb String[] age age public class Main {
	public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	}
} public class Main {
	public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	}
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] age)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer sb = new StringBuffer();

		while( true ){
			int n = Integer.parseInt(br.readLine());
			int i = 0;
			double m = 0;
			double a = 0;

			if( n==0 ) break;

			String[] s = br.readLine().split(" ");

			for( i=0 ; i<n ; i++ ){
				m = m+Double.parseDouble(s[i]);
			}

			m = m/n;

			for( i=0 ; i<n ; i++ ){
				a = a+Math.pow(Double.parseDouble(s[i])-m, 2);
			}

			a = Math.sqrt(a/n);
			sb.append(String.format("%.6f", a)).append("\n");
 		}

		System.out.print(sb);
	}
}