import Control.Applicative

main :: IO ()
main = do
    [n, a, b] <- (map read . words) <$> getLine
    print $ mod ((pow 2 n) - 1 - comb n a - comb n b) prime

pow :: Int -> Int -> Int
pow x n
    | n == 0 = 1
    | mod n 2 == 0 = pow (mod (x * x) prime) (div n 2)
    | otherwise = mod (x *  pow x (n - 1)) prime

fact :: Int -> Int
fact 1 = 1
fact n = n * fact (n - 1)

comb :: Int -> Int -> Int
comb n r = do
     (denominator n r) * (pow (numerator n r) (prime - 2))

modMul :: Int -> Int -> Int
modMul x y = mod (x * y) prime

denominator :: Int -> Int -> Int
denominator n r = foldl modMul 1 [n - r + 1..n]

numerator :: Int -> Int -> Int 
numerator n r = foldl modMul 1 [2..r]

prime :: Int
prime = 10 ^ 9 + 7
