import java.util.Scanner;

public class Main{
public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
}
} import java.util.Scanner; Scanner java.util public class Main{
public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
}
} Main public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
} main {
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n; n int[] s = new int[1000]; s new int[1000] 1000 while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
} true {
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
} double m=0 m 0 l=0 l 0 a2; a2 n = sc.nextInt() n sc.nextInt() sc.nextInt sc if(n==0) break; n==0 n 0 break; for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  } int i=0; int i=0; i 0 i<n i n i++ i++ i {
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  } {
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  } s[i] = sc.nextInt() s[i] s i sc.nextInt() sc.nextInt sc m += s[i] m s[i] s i l += s[i]*s[i] l s[i]*s[i] s[i] s i s[i] s i m /=n m n l /=n l n a2 = l-m*m a2 l-m*m l m*m m m System.out.printf("%f\n",Math.sqrt(a2)) System.out.printf System.out System System.out "%f\n" Math.sqrt(a2) Math.sqrt Math a2 sc.close() sc.close sc String[] args args public class Main{
public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
}
} public class Main{
public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
}
} Main
import java.util.Scanner;

public class Main{
public static void main(String[] args){
  Scanner sc = new Scanner(System.in);
  int n;
  int[] s = new int[1000];
 
  while(true){
  double m=0,l=0,a2;
  n = sc.nextInt();
  if(n==0) break;
  for(int i=0;i<n;i++){
    s[i] = sc.nextInt();
    m += s[i];
    l += s[i]*s[i];
  }
    m /=n;
    l /=n;
    a2 = l-m*m;
    System.out.printf("%f\n",Math.sqrt(a2));
}
  sc.close();
}
}
