{-# LANGUAGE BangPatterns #-}


import qualified Data.Vector.Unboxed as U
import qualified Data.Vector as V
import qualified Data.ByteString.Char8 as C
import Debug.Trace
import Data.List
import Control.Monad
import Data.Ord
import qualified Data.Sequence as Seq
import qualified Data.IntSet as IS
import qualified Data.Set as S

r :: Int -> IO (U.Vector Int)
r n = U.unfoldrN n (C.readInt . C.dropWhile (==' ')) <$> C.getLine

r' :: IO [Int]
r'  =   unfoldr    (C.readInt . C.dropWhile (==' ')) <$> C.getLine

rp :: IO (Int,Int)
rp  = toTup . unfoldr    (C.readInt . C.dropWhile (==' ')) <$> C.getLine

toTup [a,b] = (a,b)


mdl :: Num a => a
mdl = 10^9 + 7

main :: IO ()
main = do
    [n,a,b] <- r' :: IO [Int]
    -- naïve
    let al = (2^n - 1 :: Integer) `mod` mdl
    let na = choose n a `mod` mdl
    let nb = choose n b `mod` mdl
    -- print al
    -- print na
    -- print nb
    print $ al - na - nb `mod` mdl


choose :: Int -> Int -> Integer
choose n i = div (V.product $ ctest n i) (V.product $ V.generate i (fromIntegral.succ))

ctest :: Int -> Int -> V.Vector Integer
ctest n i = V.generate i (fromIntegral.(+ (n-i+1)))

prod' :: V.Vector Integer -> Integer
prod' = V.foldl' (\ac x -> ac * x `mod` mdl) 1


