import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
 
public class Main {
	public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    }
  
    public static void main(String[] args) throws IOException {
        new Main().exec();
    }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.PrintWriter; PrintWriter java.io public class Main {
	public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    }
  
    public static void main(String[] args) throws IOException {
        new Main().exec();
    }
} Main public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    } exec {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        } true {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/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; int[] sary = new int[n]; sary new int[n] n double avg=0 avg 0 var=0; var 0 int i=0; i 0 for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	} String s br.readLine().split(" ") br.readLine().split br.readLine() br.readLine br " " {
        		avg += sary[i++] = Integer.parseInt(s);
        	} {
        		avg += sary[i++] = Integer.parseInt(s);
        	} avg += sary[i++] = Integer.parseInt(s) avg sary[i++] = Integer.parseInt(s) sary[i++] sary i++ i Integer.parseInt(s) Integer.parseInt Integer s avg /= n avg n for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	} int s sary {
        		var += Math.pow(s - avg,2);
        	} {
        		var += Math.pow(s - avg,2);
        	} var += Math.pow(s - avg,2) var Math.pow(s - avg,2) Math.pow Math s - avg s avg 2 out.printf("%.4f\n",Math.sqrt(var/n)) out.printf out "%.4f\n" Math.sqrt(var/n) Math.sqrt Math var/n var n out.flush() out.flush out public static void main(String[] args) throws IOException {
        new Main().exec();
    } main {
        new Main().exec();
    } new Main().exec() new Main().exec new Main() String[] args args public class Main {
	public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    }
  
    public static void main(String[] args) throws IOException {
        new Main().exec();
    }
} public class Main {
	public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    }
  
    public static void main(String[] args) throws IOException {
        new Main().exec();
    }
} Main
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
 
public class Main {
	public void exec() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        while(true) {
        	int n = Integer.parseInt(br.readLine());
        	if(n==0) break;
        	int[] sary = new int[n];
        	double avg=0, var=0;
        	int i=0;
        	for(String s: br.readLine().split(" ")) {
        		avg += sary[i++] = Integer.parseInt(s);
        	}
        	avg /= n;
        	for(int s: sary) {
        		var += Math.pow(s - avg,2);
        	}
        	out.printf("%.4f\n",Math.sqrt(var/n));
        }
        out.flush();
    }
  
    public static void main(String[] args) throws IOException {
        new Main().exec();
    }
}