import java.util.ArrayList;
import java.util.Scanner;
public class StandardDeviation {
public static void main(String[] args) {
ArrayList<Double> result = new ArrayList<Double>();
ArrayList<Integer> scores = new ArrayList<Integer>();
//メソッドに分割できるがいい名前が思いつかない
Scanner sc = new Scanner(System.in);
while(sc.hasNext()){
int n = sc.nextInt();
if(n == 0){
break;
}
setInputsToList(n, sc, scores);
result.add(getDeclination(scores));
scores.clear();
}
//標準偏差の出力
for(int i = 0; i < result.size(); i++){
System.out.println(result.get(i));
}
}
private static void setInputsToList(int n, Scanner sc, ArrayList<Integer> list){
for(int i = 0; i < n; i++){
list.add(sc.nextInt());
}
}
private static double getAverage(ArrayList<Integer> list){
double result = 0;
for(int i = 0; i < list.size(); i++){
result = result + list.get(i);
}
return result / list.size();
}
private static double getSum(ArrayList<Integer> list){
double result = 0;
double avg = getAverage(list);
for(int i = 0; i < list.size(); i++){
result = result + (list.get(i) - avg) * (list.get(i) - avg);
}
return result;
}
public static double getDeclination(ArrayList<Integer> list){
return Math.sqrt(getSum(list) / list.size());
}
}