input_lines = gets.chop.split.map(&:to_i)

setNumber = 0
answer = 0 
if input_lines[0] % 2 == 0 
    setNumber =  input_lines[0]/2
else
    setNumber =  input_lines[0]/2 + 1
end

puts  setNumber * 1.0 /input_lines[0] 