import Text.Printf
main = do
    line <- getLine
    printf "%f\n" $ no211 $ read line

no211 :: Int -> Double
no211 k = (fromIntegral $ length $
        filter (\x -> x == k) [x * y | x <- sosuSai, y <- gosuSai]) /
        fromIntegral (length sosuSai * length gosuSai)

sosuSai = [2, 3, 5, 7, 11, 13] :: [Int]
gosuSai = [4, 6, 8, 9, 10, 12] :: [Int]