import java.util.Scanner;

public class Main{
  public static void main(String[] args){
    try(Scanner sc = new Scanner(System.in)){
        while(true){
                int num = sc.nextInt();
                double score[] = new double[num];
                double ave = 0;
                double var = 0;
            if(num==0)
              break;
            for(int i=0;i<num;i++){
                score[i] = sc.nextInt();
                ave = ave + (score[i]/num);
            }

            for(int i=0;i<num;i++){
                var = var + ((score[i] - ave)*(score[i] - ave) / num);
            }
            System.out.printf("%s\n",Math.sqrt(var));
        }
        }
  }
}


/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