num = gets.chomp.to_f
prime_number = [2, 3, 5, 7, 11, 13]
composite_number = [4, 6, 8, 9, 10, 12]
product = Array.new

for i in prime_number do
	for j in composite_number do
		product << i * j
	end
end

printf "%.17f", product.count(num).to_f / 36