#標準偏差を求めるプログラム（Standard Deciation）
while
    inputtimes = gets.to_i do

    break if inputtimes == 0

        inputnumbers = gets.split.map(&:to_f)
        countadd = inputnumbers.
                   inject{|e,f|e+f}
               
        count2=countadd/inputtimes
    
        finalcount= inputnumbers.
                    inject(0){|sum, i| sum + (i - count2) ** 2 }
        sum =Math.sqrt(finalcount / inputtimes)
    puts sum


end
#https://en.wikipedia.org/wiki/Standard_deviation
