# your code goes here
a=[2,3,5,7,11,13]
b=[4,6,8,9,10,12]

c=Hash.new(0)
a.each do |e1|
	b.each do |e2|
		c[e1*e2]+=1
	end
end
n=STDIN.gets.to_i
puts c[n]/36.0