def inp() a=gets.chomp.split(" ").map(&:to_i)end 
def inpf() a=gets.chomp.split(" ").map(&:to_f)end
def inps() a=gets.chomp.split(" ")end  
def copy(a) Marshal.load(Marshal.dump(a)) end
def kaizyo(n)(n < 2)? 1 : (2..n).inject(:*) end
def scount(a,b) a.each{|n|b[n]+=1} end
def na(n,d=0) Array.new(n,d)end
def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end
def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end
s = [2,3,5,7,11,13]
g = [4,6,8,9,10,12]
c = 0
k = inp[0]
s.each do |sd|
  g.each do |gd|
    c += 1 if(sd*gd == k)
  end
end
p c / (s.size*g.size).to_f