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