-- Ω\・8・)ﾁｭｰﾝ

import Control.Monad
import Text.Printf
    
main = do
  [p, c] <- liftM (map read . words) getLine
  let
    s = sum $ (*) <$> (map product (replicateM p [2,3,5,7,11,13])) <*> (map product (replicateM c [4,6,8,9,10,12]))
    e :: Double
    e = fromIntegral s / (6 ** fromIntegral (p + c))
   in printf "%.13f\n" e