m = 10^9 + 7 :: Int

modpow :: Int -> Int -> Int
modpow a n
    | n == 1 = a `mod` m
    | otherwise = (if n `mod` 2 == 1
                  then a * modpow (a `mod` m)  (n-1)
                  else modpow (a*a `mod` m) (n `div` 2)) `mod` m

fact :: Int -> Int -> Int
fact x y
    | x == y = y
    | otherwise = x * fact (x - 1) y `mod` m

nCr :: Int -> Int -> Int
nCr n r = ((fact n (n-r+1)) * modpow (fact r 1) (m - 2) ) `mod` m

main :: IO()
main = do
  [n,a,b] <- map read . words <$> getLine
  print $ ((modpow 2 n) - 1 - nCr n a - nCr n b) `mod` m