import Text.Printf (printf)

prob :: Int -> Double
prob k = flip (/) 36.0 $
    sum [1.0 | p <- [2, 3, 5, 7, 11, 13], c <- [4, 6, 8, 9, 10, 12], p * c == k]

main :: IO ()
main = printf "%.20f\n" . prob =<< readLn