n = gets.chomp!.to_i
num = []
for i in 1..n do
  num << i
end
#p num
count = 0
num.each do |e|
  if e.to_i % 2 != 0
    count += 1
  end
end
#p count

a = count.to_f / num.size
#p sprintf("%.6f", a)
#if count%num.length == 0
print(a.to_s + "000000000\n")