/**
 * Matt Kretchmar
 * February 20, 2006
 * ExamStats.java
 * This program computes the mean and standard deviation
 * for an array of integers.
 * 
 * Example:
 * Exam scores are 99 95 93 94 92 91 91 89 87 87 86 85 70 66 63
 * with mean = 85.87, std = 10.47
 */

import java.util.Scanner;

class ExamStats
{
    public static void main ( String [] args )
    {
        Scanner keyboard = new Scanner(System.in);
        
        // first scan in n to indicate how many numbers in array
        int n = keyboard.nextInt();
        
        // next scan in n numbers to store in our array
        int scores[] = new int[n];
        for ( int i = 0; i < n; i++ )
        {
            scores[i] = keyboard.nextInt();
        }
        
        // now we compute the mean
        double mean = 0;
        for ( int i = 0; i < n; i++ )
            mean += scores[i];
        mean = mean / scores.length;
        
        // now we compute the std
        double std = 0;
        for ( int i = 0; i < n; i++ )
            std += (mean - scores[i]) * ( mean - scores[i]);
        std = Math.sqrt(std / scores.length);
        
        System.out.println("mean = " + mean + ", std = " + std + ".");
    }
}