n = io.read("*n")
if(n <= 5) then print(0) else
    t = {1, 0, 0, 0, 0, 0}
    for i = 2, n do
        t[1], t[2], t[3], t[4], t[5], t[6]
        =
        t[1] * 1 / 6,
        t[1] * 5 / 6 + t[2] * 2 / 6,
        t[2] * 4 / 6 + t[3] * 3 / 6,
        t[3] * 3 / 6 + t[4] * 4 / 6,
        t[4] * 2 / 6 + t[5] * 5 / 6,
        t[5] * 1 / 6 + t[6]
        if(0.99999999 < t[6]) then break end
    end
    print(t[6])
end