module Main where
 
import Data.Function (on)
 
main :: IO ()
main = getIntList >>= print . solve
 
solve :: [Int] -> Double
solve [m, n] = ave $ go n [m]
 
ave :: [Int] -> Double
ave = on (/) fromIntegral <$> sum <*> length
 
go :: Int -> [Int] -> [Int]
go 0 xs = xs
go n xs = go (n - 1) $ do
  x <- xs
  [x * 2, x + 1, 0]
 
getIntList :: IO [Int]
getIntList = map read . words <$> getLine