import java.util.Scanner;

/**
 * @author kawakami
 *
 */
class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner as = new Scanner(System.in);
		
		int num;
		double hen = 0;
		double sum = 0;
 		double hei = 0;
		double ten[];
		
		String str;
		
		
		
		while(true){
		
		
			num = as.nextInt();
			
			if(num == 0){
				
				break;
				
			}
			
			ten = new double[num];
			
			for(int i=0;i<num;i++){
							
				ten[i] = as.nextDouble();
				hei = hei + ten[i];
				
			}
			
			hei = hei / num;
			//System.out.println(hei);
			
			for(int i=0;i<num;i++){
				
				//System.out.println(ten[i]-hei);
				sum = sum + (ten[i]-hei)*(ten[i]-hei);
				
			}
			//System.out.println(sum);
			
			hen = Math.sqrt(sum/num);
			str = String.valueOf(hen);
			System.out.println(str);
			hei = 0;
			sum = 0;
			hen = 0;
			
			
		}
		
		
		
	}

}
/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