import java.util.*;
 
public class Main {
    public static void main( String args[] ) {
        Scanner scan = new Scanner( System.in );
		
		while( true ) {
			int studentNum = scan.nextInt();
			
			if ( studentNum == 0 ) {
				break;
			}

			int[] point = new int[studentNum];
			
			// input, calculate sum
			int sum = 0;
			for( int i = 0; i < studentNum; i++ ) {
				point[i] = scan.nextInt();
				sum += point[i];
				
			}
			
			// calculate average
			double average = (double)sum / (double)studentNum;
			
			// calculate variance
			double variance = 0;
			for( int i = 0; i < studentNum; i++ ) {
				double deviation	=	point[i]	- average;
				variance			+=	deviation	* deviation;

			}
			variance = variance / studentNum;
			
			// calculate standardDeviation
			double standardDeviation = Math.sqrt( variance );
			
			System.out.println( standardDeviation );
		}
		
	}
}
/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