k = gets.chomp.to_i
ans = Array.new(20,0)
ans.size.times.with_index do |d, i|
  ans[d] = 1
  i-=1
  while(0 <= i and (d - 7) < i )
    ans[d] += ans[i] / 6.0 
    i-=1
  end
end
p ans[k-1]