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();
}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz