{-# LANGUAGE BangPatterns #-}

main :: IO ()
main = do
  [n,a,b] <- map read . words <$> getLine :: IO [Integer]
  let ala = f 2 n - 1
      nca = nCk n a
      ncb = nCk n b
  print $ (ala - nca - ncb) `mod` (10^9 + 7)

nPk :: Integral a => a -> a -> a
nPk !n' !k' = go 1 n' k'
  where go a _ 0    = a
        go !a !n !k = go ((a * n) `mod` (10^9+7)) (n - 1) (k - 1)

nCk :: Integral a => a -> a -> a
nCk !n !k = nPk n k * f (nPk k k) (10^9+7-2)

f :: Integral a => a -> a -> a
f !x 1 = x
f !x !k
  | k `mod` 2 == 0 = f ((x ^ 2) `mod` (10^9+7)) (k `div` 2)
  | otherwise = x * f ((x ^ 2) `mod` (10^9+7)) (k `div` 2)
