import java.util.Scanner;
class Main{
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        int n;
        int[] ary;
        double m, a2, sub;
        while(true){
            n = scanner.nextInt();
            if(n == 0)break;
            ary = new int[n];
            m = 0;
            a2 = 0;
            for(int i = 0; i < n; i++){
                ary[i] = scanner.nextInt();
                m += ary[i];
            }
            m /= n;
            for(int i = 0; i < n; i++){
                sub = ary[i] - m;
                a2 += sub*sub;
            }
            a2 /= n;
            System.out.println(Math.sqrt(a2));

        }

    }
}


/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