a = Array.new(206, 1.0)
b = Array.new(206, 0.0)
a[5] = 0
b[5] = 0
6.upto(205){|i|
    a[i] = a[(i - 6)..(i - 1)].inject(:+) / 6
    b[i] = b[(i - 6)..(i - 1)].inject(:+) / 6 + 1
    }
n = gets.to_i
if n <= 200
    p b[n + 5] / (1 - a[n + 5])
else
    p n + 1 + 2.0 / 3
end