import Control.Arrow
import Control.Monad
import Data.List
import qualified Data.ByteString.Char8 as B

main :: IO ()
main = readLine >>= print . solve

solve :: [Int] -> Int
solve [n, d] 
        | m > 0 = r + 1
        | otherwise = r
        where 
            (r, m) = n `divMod` (d * 2 + 1)

readLine :: IO [Int]
readLine = unfoldr (fmap (second (maybe B.empty snd . B.uncons)) . B.readInt) <$> B.getLine

readContents :: Int -> IO [[Int]]
readContents = flip replicateM readLine