#!/usr/bin/env ruby

number = gets.to_f
points = gets.split.map(&:to_i)
ppoints = []
variance = 0

points.each do |p|
    2jou +=  p ** 2
    ave += p
end

ave = (ave / number) ** 2
2jou = 2jou / number

variance = 2jou - ave
standard_deviation = (variance) ** 2.0
