main = do
  [n, a, b] <- map read.words <$> getLine
  print $ solve n a b

solve n a b = (2 ^% n) -% comb n a -% comb n b -% 1

mo = 10^9 + 7 :: Int
a ^% b
  | b < 0 = 0
  | b == 0 = 1
  | otherwise = f a b
  where
    f a b
      | even b = f (a *% a) (quot b 2)
      | b == 1 = a
      | otherwise = g (a *% a) (quot b 2) a
    g a b c
      | even b = g (a *% a) (quot b 2) c
      | b == 1 = a *% c
      | otherwise = g (a *% a) (quot b 2) (a *% c)
a *% b = rem (a * b) mo
a /% b = a *% (b ^% (mo - 2))
comb a b = foldl (*%) 1 [a-b+1..a] /% foldl (*%) 1 [1..b]
a -% b = rem (mo + a - b) mo